The 20:4 schedule

What 20:4 means

20 hours not eating, a 4 hour eating window, adding up to the full day. It's sometimes described alongside the "Warrior Diet" style of eating, though the schedule itself is just a ratio of hours, nothing more. Most of your day sits outside the window; the window itself is a focused block, often one main meal plus something smaller.

How the timer helps

A 4 hour window doesn't leave much room to lose track of time. If you check the clock and you're already an hour into the window without realizing it, that's a quarter of it gone. WhenCanIEat keeps the countdown visible until the window opens, then switches to counting down how much of the window remains, so there's no ambiguity about how much time is actually left to eat.

An example day

Here's a 20:4 schedule with an eating window from 2:00 PM to 6:00 PM:

Time	What's happening
6:00 PM (previous day)	Eating window closes, fast begins
Overnight	Fast continues through sleep
10:00 AM	Timer shows the countdown to your window opening
2:00 PM	20 hour fast complete, eating window opens
2:00 PM to 6:00 PM	Eating window is open
6:00 PM	Window closes, next fast begins, streak updates

Because the window is short, many people place it around whichever single meal already anchors their day, whether that's a late lunch or an early dinner.

Why the notice before closing matters

With only 4 hours open, most of the value of the App at this schedule is the reminder before the window closes rather than the reminder that it opened. Knowing you have 30 minutes left, not 3 hours, changes what you plan to do with that time.

Getting started

Open WhenCanIEat, choose the 20:4 preset, set your window start time, and start your first fast. Free to try, no account needed.