Subtract fixed time from duration field

[Zen_sbr]

Hello,
I’m trying to subtract a specific time (3:30 hours) from a duration field using formula that looks like this:
Difference field = IF({Ride duration}=3:30,0,({Ride duration}-3:30))
Basically, I want to subtract 3:30 hours from the duration field to know the difference between the times

What am I missing here?

Thanks in advance,
Liat :slightly_smiling_face:

[ScottWorld · Accepted solution]

I just posted about this a few minutes ago in another thread:

Time Tracker Block - Calculate Billable Time Dates and timezones

Welcome to the community, @David_Derby! :slight_smile: There are 2 different Airtable tricks to know about, in order to understand how to work with durations: Duration trick #1: The first trick to understanding the duration field is that Airtable only understands duration in “seconds”, not “minutes” or “hours”. So even if Airtable is visually showing you “minutes” or “hours” on the screen, Airtable is still calculating the duration in “seconds” behind-the-scenes. So, 30 minutes is equal to …

[Zen_sbr]

Thank u!!!
that helped a lot!!!