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Productivity8 min read

The Temperature Minimum (Tmin): How to Shift Your Internal Clock

To overcome jetlag or change your chronotype habits, you must understand your biological anchor point.

Your circadian rhythm is anchored by a specific physiological marker known as your Temperature Minimum (Tmin). This is the point in the 24 hour cycle when your core body temperature is at its absolute lowest.

Calculating Your Tmin

For most people, the Tmin occurs approximately two hours before their natural wake time. For example, if you naturally wake up at 7 AM, your Tmin happens right around 5 AM.

The Rule of Phase Shifting

If you want to shift your sleep schedule, you use light exposure relative to your Tmin.

**Phase Advance (Waking Earlier)**: Getting bright light exposure immediately AFTER your Tmin pulls your rhythm earlier in the day. This is how you transition into an early riser.
**Phase Delay (Staying Up Later)**: Getting bright light exposure in the hours BEFORE your Tmin pushes your rhythm later into the evening.

Understanding your specific Tmin is the ultimate key to hacking jetlag or adjusting to a new work schedule without feeling miserable.

EditorARC Scientific Team
Date Published2026-02-06

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