Mapping a 5-on/2-off cycle onto a real calendar
5-on/2-off doesn't drift the way people assume — but plenty of other cycles do, and the difference is one division away from a calendar you have to check by hand.
- A cycle counts elapsed days from an anchor date — not weekdays, even when it looks that way
- One number decides whether it drifts: (days-on + days-off) mod 7. Zero means fixed weekdays forever; anything else means the on-days shift every cycle
- 5-on/2-off has a 7-day period — once you know the start day, it never drifts; it just repeats whichever weekdays it began on
- Shorter cycles can walk through the entire week — a 4-day period only returns to its starting weekday every 28 days
- The running count belongs to your log, not the calendar — let the tool compute "day X of Y" instead of counting by hand
A calendar week resets every seven days on its own schedule. A days-on/days-off cycle resets on its own schedule too — and the two only match up when the math says they should.
A cycle counts elapsed days, not weekdays
A 5-on/2-off pattern, or any days-on/days-off cycle, counts forward from the date you started it, one day at a time, until it hits the total and starts over. It has no idea what day of the week it is. Whatever weekday relationship it ends up with is a side effect of arithmetic, not a rule it follows.
That’s different from a weekday pattern, the Monday/Wednesday/Friday kind. A weekday pattern is defined by the day of the week itself, so it repeats identically every calendar week by definition — there’s nothing to compute. A days-on/days-off cycle is defined by an anchor date and a count, and it only looks like a weekday pattern when the numbers happen to line up.
The mix-up starts here: picture a 5-on/2-off cycle that happens to begin on a Monday, and it reads as “weekdays on, weekend off” — a tidy match for the work week. Start the identical pattern on a Thursday and you get on-days that run Thursday through Monday, off-days Tuesday and Wednesday. Same rule. A different map. Neither version is drifting; they’re both just anchored somewhere else.
One number decides whether a schedule drifts
Whether a cycle keeps the same weekday map forever, or wanders to a new one every time it repeats, comes down to a single comparison: the cycle’s total length against seven.
A remainder of zero means the period is a multiple of seven, so the cycle’s on-days land on the same weekdays every single repeat, indefinitely, once you know where the first one fell. Any other remainder means the start of each new cycle shifts forward by that many days, and the on-days walk to a different stretch of the week each time.
A calendar didn't break your cycle. It was never tracking the same thing your cycle counts.
A 5-on/2-off pattern, mapped four different ways
Because 5-on/2-off has a seven-day period, the remainder above is always zero. The only thing that changes the outcome is which day you happened to start on.
| Start day | On days | Off days |
|---|---|---|
| Monday | Mon–Fri | Sat–Sun |
| Tuesday | Tue–Sat | Sun–Mon |
| Wednesday | Wed–Sun | Mon–Tue |
| Thursday | Thu–Mon | Tue–Wed |
Whichever row your start date falls into is the row you stay on. There’s no drift to plan around here — the pattern repeats that exact weekday map every week, forever, because a seven-day period fits a seven-day calendar week exactly once.
A shorter cycle walks through the whole week
Not every cycle is built from a seven-day period. Take a 3-on/1-off pattern purely as an illustration of the arithmetic — a four-day period, started on a Monday.
- Cycle 1 starts Monday. On Mon–Wed, off Thursday.
- Cycle 2 starts Friday. On Fri–Sun, off Monday.
- Cycle 3 starts Tuesday. On Tue–Thu, off Friday.
- Cycle 4 starts Saturday. On Sat–Mon, off Tuesday.
- Cycle 5 starts Wednesday. On Wed–Fri, off Saturday.
Each new cycle starts four days after the last one, and four days later is also four weekdays later — Monday, then Friday, then Tuesday, then Saturday. It takes seven cycles, 28 days, before the pattern lands back on a Monday start, because 28 is the smallest number of days that both a four-day period and a seven-day week divide into evenly. Any cycle whose period isn’t a multiple of seven does this same walk; the formula above just tells you how far each jump goes.
Letting the app hold the count
None of this is hard arithmetic. It’s arithmetic you have to redo correctly every single day, which is a different problem.
- Anchor the cycle to the date you actually started it — or restarted it, if a gap happened — not to a day of the week.
- Count the days since that anchor to get the current position in the period.
- Read the status off the position — inside the on-count means on, past it means off, and the count rolls over at the total.
- Decide, separately, what a missed day does to the count. Whether the cycle keeps running from the original anchor or restarts from the day you resumed is a schedule design question for you and whoever set the protocol, not something the calendar can answer on its own.
A paper calendar or a memorized rule breaks at step two the first time a trip, a schedule change, or a missed day interrupts the count — after that, every “which day is this” question is a guess. Amidra’s protocol builder keeps the anchor date and the period for you and shows the day position directly, so you read the status instead of recomputing it from memory, whether or not the pattern happens to land on convenient weekdays.
The days-on/days-off math above only answers when. It says nothing about how much, and if a cycle includes reconstituting a fresh vial partway through, the concentration and draw-volume formulas are the next calculation — followed by converting that draw into syringe units once the vial’s concentration is fixed.
Bottom line: let the arithmetic run itself
Cycles aren’t unpredictable. A days-on/days-off count and a weekday pattern just look identical in the one case where the math agrees, and nothing alike everywhere else. Once you know which kind of pattern you’re running, and whether its period divides evenly into seven, the calendar stops being a puzzle and turns into a lookup: anchor date, one division, read the day. The only habit worth dropping is counting cycles by hand past the first one — that’s where a single missed day quietly becomes a wrong day for weeks afterward, and Amidra is built to hold that count instead of you.
Common questions
Does a 5-on/2-off cycle always fall on the same weekdays?
Yes, once it's anchored to a start date. 5-on/2-off has a 7-day period, the same length as a calendar week, so whichever weekdays it starts on are the weekdays it repeats on, indefinitely. It only looks like it's drifting if you lost track of which day you started it.
Why do some cycles drift across the week while others don't?
It comes down to the cycle's total length — days on plus days off — compared with 7. If that total is a multiple of 7, the on-days lock to fixed weekdays forever. If it isn't, the on-days shift by the remainder every time the cycle repeats, walking to a different stretch of the week each cycle.
What happens to the day count if I miss or skip a day?
That's a scheduling decision, not a calendar fact. Whether the count keeps running from the original anchor date or restarts from the day you resumed depends on how the protocol is meant to work, which is a call for you and whoever set the schedule — Amidra recomputes the day index from whatever dates you actually log, so the count reflects your real history either way.
Can I track a plain weekday pattern instead of a days-on/days-off cycle?
Yes. A pattern like Monday/Wednesday/Friday is defined by the weekday itself, so it repeats identically every calendar week by definition — there's no mod-7 check needed. A days-on/days-off cycle is a different kind of pattern, counted in elapsed days from a start date, and the two only look the same when the cycle's period happens to be a multiple of 7.
Does Amidra decide which cycle schedule to run?
No. You set the days-on/days-off (or weekday) pattern in your protocol; Amidra does the calendar arithmetic — anchor date, weekday mapping, day count — on the pattern you enter. Every decision about which schedule to run comes from you and your clinician.
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