Zeitfarer End User License Agreement
Version 1.0 | Effective October 10, 2026
1. Agreement and acceptance
This End User License Agreement (this “Agreement”) is a binding agreement between you and McCall Aviation Consulting, LLC. It governs your use of the Zeitfarer mobile application, including its content, features, updates, and beta versions (the “App,” also called the “Service” in this Agreement). The zeitfarer.com website is covered by its own Terms of Use.
How you accept. When you first open the App, it shows you this Agreement and asks you to accept it. By selecting “I Agree,” or by installing, opening, or using the Service, you confirm that you have read, understood, and agree to be bound by this Agreement and acknowledge our Privacy Policy. If you do not agree, select “Decline,” do not use the Service, and delete the App.
New versions. If we materially change this Agreement, the App will ask you to accept the new version before you continue using it, as described in Section 25.
Organizations. If you accept on behalf of an airline, company, or other organization, you confirm that you have authority to bind it, and “you” includes that organization.
Please read the health and safety notice and the fitness-for-duty section carefully. They limit what the App is and what you may rely on it for. This Agreement also limits our liability, requires individual claims, and waives jury trial, to the extent the law allows.
2. Who we are
McCall Aviation Consulting, LLC is a Colorado limited liability company. In this Agreement, “we,” “us,” and “our” mean McCall Aviation Consulting, LLC. We provide aviation consulting services under the name McCall AvCo at mccallavco.com, and we publish the Zeitfarer app and its website at zeitfarer.com. Each has its own terms built on the same structure.
3. Eligibility
You must be at least 18 years old and able to form a binding contract to use the Service. You may not use the Service if you are barred from doing so under the laws of the United States or any other applicable country.
The App is designed for airline pilots and other flight crew members. You may use it for your own trips whether or not you are a crew member, but its assumptions reflect airline operations.
4. Important health and safety notice
The App produces schedules and suggestions for sleep, light exposure, light avoidance, meals, exercise, caffeine, and melatonin. They are based on published circadian research and on the information you enter. They are general estimates, not individualized medical recommendations. Circadian responses vary widely between people, and the App cannot measure your actual sleep, alertness, or physiology.
Not medical advice. The App is not a medical device. It does not diagnose, treat, cure, monitor, mitigate, or prevent any disease, sleep disorder, or other condition. Nothing in it is medical advice or a substitute for advice from a physician or Aviation Medical Examiner. Never disregard or delay seeking medical advice because of something in the App.
Talk to a physician first before following the App’s suggestions if you have, or think you may have, a sleep disorder (such as sleep apnea or insomnia), a heart or blood pressure condition, diabetes, epilepsy, bipolar disorder, depression, or another mood disorder, an eye or retinal condition, migraine, or any other medical condition, if you are pregnant or nursing, or if you take prescription medication. Timed bright light can affect mood and can interact with photosensitizing medication and some eye conditions.
Melatonin and supplements. Melatonin and other supplements are not regulated like medications, can cause drowsiness, and can interact with other drugs. Before using melatonin or any other supplement or medication, confirm with your physician or Aviation Medical Examiner that it is appropriate for you and permitted under FAA medical guidance, the rules of any other aviation authority that applies to you, and your employer’s policies, including any required wait before flying.
Caffeine and exercise. Follow caffeine and exercise suggestions only within limits that are safe for you.
Drowsiness. Shifting your sleep can make you drowsy at unusual times. Do not drive, fly, or operate machinery when you are drowsy.
Stop if you feel unwell. Stop following any suggestion that makes you feel unwell, and seek medical care for any concerning symptoms. In an emergency, call your local emergency number.
5. Your responsibility for fitness for duty
The App does not determine whether you are rested, alert, or fit to fly. It is not a fatigue risk assessment and does not replace:
14 CFR Part 117 or any other flight, duty, and rest regulation that applies to you;
your operator’s Fatigue Risk Management System, fatigue policies, or fatigue calling procedures;
your collective bargaining agreement; or
your own judgment.
Under 14 CFR 117.5 and similar rules, you alone are responsible for reporting for duty rested and prepared, and for reporting when you are too fatigued to continue. Do not rely on the App for any safety-critical, operational, or regulatory decision. You use the App at your own risk and assume all risks of following or not following its suggestions.
Accuracy. Schedules depend on the accuracy of what you enter, including flight times, airports, time zones, and sleep. The App may contain errors, and schedules or published times may change. We do not guarantee that any suggestion will improve your sleep, alertness, performance, or adjustment to a new time zone.
6. License grant
Subject to your compliance with this Agreement, we grant you a limited, nonexclusive, nontransferable, nonsublicensable, revocable license to download, install, and use the App on Apple-branded devices that you own or control, as permitted by the Usage Rules in Apple’s Media Services Terms and Conditions, for your personal, noncommercial use. The App may be used by other accounts associated with you through Family Sharing where Apple allows it.
The App is licensed, not sold. We and our licensors keep all ownership of the App and every copy of it.
If your employer or another organization wants to provide the App to its crew members, or to use it for commercial purposes, it needs a separate written agreement with us.
7. Restrictions and acceptable use
You agree not to, and not to help anyone else to:
use the Service in violation of any law or regulation, or in a way that infringes anyone’s rights;
copy, modify, distribute, sell, lease, or create derivative works from the Service, except as this Agreement allows;
reverse engineer, decompile, or disassemble the Service, or try to derive its source code, algorithms, models, or formulas, except to the extent the law expressly permits despite this restriction;
use robots, scrapers, crawlers, or other automated means to access, copy, or collect content from the Service;
use any part of the Service to train, test, or improve an artificial intelligence or machine learning model, or to build a competing product or service;
remove or alter any copyright, trademark, or other notice;
interfere with, disrupt, or try to gain unauthorized access to the Service or its systems; or
send spam, malware, or unlawful, harassing, or misleading content through the Service.
In addition, you may not rent, lend, sublicense, or transfer the App; make it available over a network where multiple devices could use it at once; or get around the free trip limit or the purchase requirement.
8. Free trip, purchase, and refunds
Free trip. The App includes one free trip so that you can try it.
Unlock. Continued use requires a one-time in-app purchase through Apple’s App Store. The price is shown in the App Store before you buy and may change for future buyers. Apple processes all payments, and any taxes are handled by Apple.
Restoring. Your unlock is tied to your Apple Account. You can restore it on another eligible device with Restore Purchases.
Refunds. Refunds are available only from Apple under its policies. We cannot issue refunds directly.
Beta testers. Any complimentary unlock we offer to beta testers is at our discretion and subject to the terms we announce with it.
9. Updates, changes, and availability
We may release updates and may add, change, or remove features, including the scientific models the App uses. Some updates may be required to keep using the App. We may stop offering or supporting the App at any time. If we do, the App may continue to work on your device, but we have no obligation to provide support or to keep it compatible with future devices or operating systems.
10. Beta versions
Beta and TestFlight versions are provided for testing only, may contain errors, may lose data, and may stop working at any time. Please do not rely on a beta version for real trips. Apple’s TestFlight terms also apply to beta versions.
11. Your information and your device
Everything you enter in the App is stored only on your device and is never sent to us. As a result:
you are responsible for your device, its security, and any backups;
we cannot see, recover, correct, or delete your information for you; and
deleting the App, resetting your device, or a device failure may permanently erase your information, and we are not responsible for that loss.
The App contacts Apple’s App Store only to confirm your purchase, as our Privacy Policy explains.
12. Intellectual property
The Service and everything in it, including text, articles, graphics, logos, designs, software, algorithms, models, formulas, and documentation, are owned by McCall Aviation Consulting, LLC or its licensors and are protected by copyright, trademark, trade secret, and other laws. McCall Aviation Consulting, McCall AvCo, Zeitfarer, and our logos are our trademarks. You may not use them without our written permission. We reserve all rights not expressly granted in this Agreement.
13. Your submissions and feedback
You keep ownership of what you send us. You grant us a nonexclusive, worldwide, royalty-free license to use it as needed to respond to you and to provide and operate the Service.
If you give us ideas, suggestions, bug reports, or other feedback about the Service (“Feedback”), you grant us a perpetual, irrevocable, worldwide, royalty-free license to use, modify, and incorporate that Feedback for any purpose without payment or attribution to you. You are not required to give us Feedback.
14. Aggregated and de-identified data
We may create aggregated and de-identified data from information we receive in connection with the Service (“De-identified Data”). De-identified Data cannot reasonably be used to identify you or any other person, directly or indirectly. You agree that we own all right, title, and interest in De-identified Data, and that we may use, analyze, disclose, and commercialize it for any lawful purpose, including research, statistics, product development, publications, and the creation of new services, during and after your use of the Service, without payment to you.
When we create or use De-identified Data, we will:
take reasonable technical and organizational measures to ensure it cannot be linked back to you;
not attempt to re-identify it, except as the law permits to test our de-identification methods; and
require anyone we share it with to agree in writing not to re-identify it.
This section applies only to information we actually receive. It does not give us access to anything we do not otherwise collect, as described in our Privacy Policy.
15. Privacy
Our Privacy Policy at zeitfarer.com/privacy explains what information we collect and how we use it. It is part of this Agreement.
16. Third-party services, content, and software
The Service may link to or rely on websites, content, and services owned by others. We do not control them and are not responsible for their content, accuracy, availability, or privacy practices. Your use of them is at your own risk and subject to their terms.
The App may reference published research and may include third-party or open-source software components. Those components are licensed under their own terms, which are listed in the App where required, and those terms control for those components.
17. Disclaimer of warranties
THE SERVICE IS PROVIDED “AS IS” AND “AS AVAILABLE,” WITH ALL FAULTS AND WITHOUT WARRANTY OF ANY KIND. TO THE FULLEST EXTENT PERMITTED BY LAW, WE DISCLAIM ALL WARRANTIES, EXPRESS, IMPLIED, OR STATUTORY, INCLUDING WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE, NON-INFRINGEMENT, ACCURACY, AND QUIET ENJOYMENT. WE DO NOT WARRANT THAT THE SERVICE WILL BE UNINTERRUPTED, ERROR-FREE, SECURE, OR CURRENT, OR THAT ANY INFORMATION OR RESULT IT PROVIDES WILL BE ACCURATE, COMPLETE, OR SUITED TO YOUR SITUATION.
18. Limitation of liability
TO THE FULLEST EXTENT PERMITTED BY LAW, McCALL AVIATION CONSULTING, LLC AND ITS MEMBERS, MANAGERS, EMPLOYEES, AND AGENTS WILL NOT BE LIABLE FOR ANY INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL, EXEMPLARY, OR PUNITIVE DAMAGES, OR FOR ANY LOSS OF PROFITS, REVENUE, DATA, EMPLOYMENT, CERTIFICATION, OR GOODWILL, ARISING OUT OF OR RELATING TO THE SERVICE OR THIS AGREEMENT, WHETHER IN CONTRACT, TORT (INCLUDING NEGLIGENCE), STRICT LIABILITY, OR ANY OTHER THEORY, EVEN IF WE HAVE BEEN ADVISED OF THE POSSIBILITY OF THOSE DAMAGES.
OUR TOTAL LIABILITY FOR ALL CLAIMS ARISING OUT OF OR RELATING TO THE SERVICE OR THIS AGREEMENT WILL NOT EXCEED THE GREATER OF (A) THE AMOUNT YOU PAID FOR THE SERVICE IN THE TWELVE MONTHS BEFORE THE CLAIM AROSE, OR (B) ONE HUNDRED U.S. DOLLARS ($100).
Some jurisdictions do not allow certain warranty exclusions or liability limits, so some of the above may not apply to you. In that case, our liability is limited to the smallest amount the law allows.
19. Indemnification
You agree to defend, indemnify, and hold harmless McCall Aviation Consulting, LLC and its members, managers, employees, and agents from any claims, damages, losses, liabilities, costs, and expenses, including reasonable attorneys’ fees, arising out of or relating to (a) your use or misuse of the Service, (b) your violation of this Agreement, (c) your violation of any law or the rights of any third party, or (d) any decision you make or action you take in reliance on the Service.
20. Governing law and disputes
Governing law. This Agreement and any dispute arising out of or relating to it or the Service are governed by the laws of the State of Colorado, without regard to its conflict of laws rules.
Informal resolution first. Before filing any claim, you agree to contact us in writing and try in good faith to resolve the dispute for at least 30 days.
Venue. Any claim must be brought exclusively in the state courts located in Arapahoe County, Colorado, or the United States District Court for the District of Colorado, and you consent to the personal jurisdiction of those courts. Either party may bring an eligible claim in small claims court.
Time limit. Any claim must be filed within one year after it arises, or it is permanently barred, to the extent the law allows.
Individual claims only. To the extent permitted by law, claims may be brought only on an individual basis and not as a plaintiff or class member in any class, collective, or representative action.
Jury waiver. TO THE EXTENT PERMITTED BY LAW, YOU AND WE EACH WAIVE THE RIGHT TO A TRIAL BY JURY.
21. Term and termination
This Agreement is effective when you accept it and continues until terminated. You may end it at any time by deleting the App. Your license ends automatically, without notice, if you fail to comply with this Agreement. We may also suspend or end your access to the Service if we stop offering it.
When this Agreement ends, you must stop using the App and delete all copies. Sections 12 through 20 and 26, and any other terms that by their nature should survive, will survive termination.
22. Terms required by Apple
If you downloaded the App from Apple’s App Store, you and we acknowledge the following:
This Agreement is between you and McCall Aviation Consulting, LLC only, and not with Apple Inc. (“Apple”). We, not Apple, are solely responsible for the App and its content.
Your license is limited to use on Apple-branded products that you own or control, as permitted by the Usage Rules in Apple’s Media Services Terms and Conditions, except that the App may be accessed by other accounts associated with you through Family Sharing or volume purchasing.
Apple has no obligation to provide any maintenance or support for the App.
If the App fails to conform to any applicable warranty, you may notify Apple, and Apple will refund the purchase price for the App to you. To the maximum extent permitted by law, Apple has no other warranty obligation with respect to the App. Any other claims, losses, liabilities, damages, costs, or expenses attributable to any failure to conform to any warranty are our responsibility, to the extent not disclaimed in this Agreement.
We, not Apple, are responsible for addressing any claims by you or a third party relating to the App or your possession or use of it, including product liability claims, claims that it fails to conform to any legal or regulatory requirement, and claims under consumer protection, privacy, or similar laws.
If a third party claims that the App or your possession or use of it infringes that party’s intellectual property rights, we, not Apple, are solely responsible for the investigation, defense, settlement, and discharge of that claim.
You represent that you are not located in a country subject to a U.S. government embargo or designated by the U.S. government as a “terrorist supporting” country, and that you are not listed on any U.S. government list of prohibited or restricted parties.
You must comply with applicable third-party terms when using the App.
Apple and its subsidiaries are third-party beneficiaries of this Agreement, and once you accept it, Apple will have the right, and will be deemed to have accepted the right, to enforce this Agreement against you as a third-party beneficiary.
Questions, complaints, or claims about the App should be sent to us at the address in Section 27.
23. U.S. Government end users
The App is a “commercial item” as defined in 48 C.F.R. 2.101, consisting of “commercial computer software” and “commercial computer software documentation.” Consistent with 48 C.F.R. 12.212 and 48 C.F.R. 227.7202, all U.S. Government end users acquire the App only as a commercial item and with only those rights granted to all other end users under this Agreement.
24. Your rights under local law
Some countries and states give consumers rights that cannot be waived or limited by contract. Nothing in this Agreement limits those rights. Where local law does not allow a provision of this Agreement, that provision applies only to the extent the law allows.
25. Changes to this Agreement
We may update this Agreement from time to time. When we do, we will post the new version at zeitfarer.com/eula and change the effective date. For material changes, the App will ask you to review and accept the new version before you continue using it. Otherwise, changes take effect 30 days after posting. Changes will not apply to a dispute that arose before they were posted.
26. General terms
Entire agreement. This Agreement, together with our Privacy Policy and any other terms referenced here, is the entire agreement between you and us about the Service. If you signed a separate written agreement with us that covers the App, that agreement controls where it conflicts with this one.
Severability. If any provision is found unenforceable, it will be enforced to the maximum extent permitted and the rest of this Agreement will remain in effect.
No waiver. Our failure to enforce any provision is not a waiver of our right to enforce it later.
Assignment. You may not assign or transfer this Agreement without our written consent. We may assign it, including in connection with a merger, sale, or reorganization.
Events beyond our control. We are not liable for any delay or failure caused by events beyond our reasonable control.
Export and sanctions. You represent that you are not located in a country subject to a U.S. government embargo or designated as a “terrorist supporting” country, and that you are not on any U.S. government list of prohibited or restricted parties. You will not export or use the App in violation of U.S. export laws.
Electronic communications. You agree that we may communicate with you electronically, and that electronic notices and your electronic acceptance of this Agreement satisfy any requirement that they be in writing.
Headings. Headings are for convenience only and do not affect interpretation.
27. Contact
McCall Aviation Consulting, LLC
8235 S Vandriver Way
Aurora, CO 80016
Email: support@zeitfarer.com