What the swap check looks at
- Double-booking: the shift each of you picks up can't overlap another of that person's shifts, including shifts at your other jobs if you add those calendars.
- Rest: the hours between the shift you pick up and your shifts just before and after it, and the same for your colleague. You set the minimum: 8, 10, 11 or 12 hours, or as long as the shift before it, the emergency medicine residents' rule.
- Giving a shift away or covering one: pick "Nothing" on one side. Then only the person picking up a shift is checked.
- Which of their upcoming shifts would work with the shift you give away, and which of yours they could take.
Only shifts in the calendars count, and entries of 3 hours or more, such as a conference block, count as shifts. Shifts named call, like "Night call" or "24-hour call", count too. On call, backup, standby, jeopardy and sick call, and entries under 3 hours, are set aside until you tick the box under that calendar, which lists them. All-day entries, such as vacation or a week off, are skipped: they have no start or end time.
For residents
- Tick the box to check the ACGME duty-hour rules for both of you, before and after the swap: 80 hours a week averaged over 4 weeks, one day off in seven, 24 hours of continuous work plus up to 4 for handoffs, 14 hours off after 24-hour call, and call no more than every third night. You see what the swap would break, what it would make worse, and what was already broken, coming up or past.
- Emergency medicine adds its own limits: shifts of 12 hours at most, rest after each shift at least as long as the shift, 72 hours a week in all, and one full day off every week, not averaged. Picking it switches the minimum rest to as long as the shift. The 60-hour limit on hours seeing emergency department patients passes when your scheduled hours are 60 or fewer; above that, a calendar can't tell patient time from conferences and other work. Internal medicine adds its night float limits.
- Averages use whole 4-week blocks from the day your rotation started, if you enter it, or from the Monday 4 weeks before the swap. The result says which weeks it checked, and warns when either of you has no shifts in for part of them. The ACGME leaves vacation and other leave out of its averages; the check skips vacation days but still averages over the whole block, so a block with vacation in it reads low.
- In-house call counts toward every rule. If your call was set aside as on call, tick the box under that calendar to count it.
To check every block on your calendar, not only the weeks around a swap, use the duty-hour check.
Where to find a calendar link or file
In your scheduling app, look for Sync, Subscribe, iCal or Calendar feed, and copy the link that starts with webcal:// or https://, or download the .ics file. If your shifts are in another calendar, these pages show where to look: Google Calendar, Outlook and Apple Calendar, and how to export a calendar file.
What happens to the calendars
Capillary Health, which makes scheduling software for hospitals and clinics, runs this check for free, with no account needed. It isn't connected to any hospital or department that uses Capillary.
A calendar file stays on your device: your browser reads it. Shifts you type stay on your device too.
For a calendar link, Capillary's server fetches the calendar once and reads entry names only to set aside on call, backup and sick call, and meetings and other short entries. It sends your browser each entry's start and end time and which ones it set aside, never names, places or notes. The server keeps neither the link nor the shifts, and doesn't log the link.
Your browser does all the checking. The results stay on this page: Capillary doesn't save them or send them to anyone, including your employer, program or department.
Anyone who has a calendar link can see the shifts in it, so don't post one anywhere public.
Common questions
- Do I need my colleague's calendar?
- No. Typing their shifts for the week or two around the swap is enough. For the duty-hour check, add their shifts for the weeks the result says it checked. If you use their calendar link or file, ask them first.
- Why 11 hours to start?
- It's the cutoff fatigue research uses: with less than 11 hours off, people sleep less before the next shift. The other checks on this site use it too. The ACGME says residents should have at least 8 hours off, and emergency medicine residents need rest at least as long as the shift before it; picking emergency medicine switches to that rule. Pick the rule your program, group or hospital uses.
- Can I give a shift away, or cover one, with nothing in return?
- Yes. To give yours away, pick "Nothing" as the shift you pick up. To cover one of theirs, pick "Nothing" as the shift you give away. Only the person picking up a shift is checked.
- What about the night the clocks change?
- A shift across a clock change counts its real hours. In 2026 the clocks fall back on Sunday, November 1, so a 19:00 to 07:00 night that weekend is 13 hours, and for emergency medicine residents it reads as over the 12-hour limit.