Our school district uses O365 Sharepoint in the cloud. I've been tasked with creating a calendar in Sharepoint for all users for conference rooms reservations. I have NO experience with Sharepoint. Most of this has been rather straightforward but I've hit a bump in the road.

I have a calculated column to figure out what the prep time is that the user needs so that it is shown on the calendar with the meeting request.

=[Start Time]-([Prep Hours]/24+[Prep Minutes]/1440)

This worked fine until one of our testers added a meeting that had NO prep time and then everything (workflows, adding it to the calendar) failed and he got an error.

I'm trying to account for a meeting with no prep time and have tried several (like 25+) different ways but keep getting a syntax error when I try to save it.

This is my latest - =[Start Time]-([Prep Hours]/24+[Prep Minutes]/1440), "[Start Time]")

I initially tried this one with ELSE which did not work.

Could someone please guide me to the enlightened path, please, where the calculated field will take into account a request WITH prep time and also without?

ETA - I'm not a programmer, nor do I have Sharepoint training, so unfortunately, I'm rather in the dark here.

  • I started out using this - =IF([Prep Hours]+[Prep Minutes]=0, THEN[Start Time]=[Start Time]) ELSE [Start Time]-([Prep Hours]/24+[Prep Minutes]/1440)
    – Deb
    Jun 1, 2020 at 20:38
  • Tried this - =IF (ISBLANK ([Prep Hours]),ISBLANK([Prep Minutes])&"-"[Start Time])
    – Deb
    Jun 1, 2020 at 20:39

1 Answer 1


I was able to figure this out.

Here's the formula I used:

=IF(AND(VALUE([Prep Hours])=0,VALUE([Prep Minutes])=0),"[Start Time]",[Start Time]-([Prep Hours]/24+[Prep Minutes]/1440))

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