Microsoft Power Apps Canvas Apps, Power Fx Formulas, and Controls
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To save a date to SharePoint with Patch, pass a Date to a date-only column and a DateTime to a date-and-time column, as values, not text. SharePoint then shows exactly what the person chose, as long as the site's time zone is the one they work in. A night shift saved this way showed as 24/10/2026 22:00 to 25/10/2026 06:00.
Saving to SharePoint takes a moment, and a second tap on Save in that moment runs its formula again: two items instead of one. Make setting a context variable the first thing OnSelect does, keep the button disabled and showing Saving... while the variable is true, and set it back when the save finishes, whether it worked or not.
When a screen is built from separate controls and saved with Patch, nothing checks the values for you. Two pieces do the job: a message that shows the first thing wrong, and a Save button that stays disabled until every field is filled in and there's nothing wrong. Put the rules in one place, and both pieces use them.
Two time ranges overlap when each one starts before the other ends. In a formula, that's StartTime < NewEnd && EndTime > NewStart. Put it in a LookUp on your list and you get the first entry that clashes with a new one, or blank when the time is free.
A user-defined function is a formula with a name and parameters. You write it once in App.Formulas, then call it from any control, exactly like a built-in function: ShiftMinutes(Date(2026, 10, 24), Time(22, 0, 0), Time(6, 0, 0)) returns 540. Change the function, and every control that calls it changes with it.
Durations are easiest to count in minutes, and easiest to read in hours. 450 minutes is 7 h 30 min: RoundDown gives the whole hours and Mod the minutes left over. As decimal hours, the way payroll usually wants them, it's 7.50: divide by 60 and format with Text(..., "0.00").
Power Apps has three functions that round a number to the decimal places you choose. Round goes to the nearest value, RoundDown always goes down and RoundUp always goes up. 445 minutes is 7.4166… hours: Round(445 / 60, 2) makes it 7.42.
Mod returns what's left over after a division. Mod(450, 60) is 30: 450 minutes is seven whole hours with 30 minutes left over. Together with RoundDown for the whole hours, it turns a number of minutes into hours and minutes.
TimeZoneOffset tells you how many minutes the user's local time is from UTC at a given moment. Add that number to a local time with DateAdd and you have UTC: in London, 09:00 on 1 July is 08:00 UTC. Pass the moment you're converting, because daylight saving changes the offset.
Twice a year, a night shift is not the length its clock times suggest. When UK clocks go back in October, 22:00 to 06:00 is nine real hours; when they go forward in March, it's seven. Build the start and finish as real moments with DateTime and count minutes with DateDiff, and Power Apps counts the real time on both nights.
