Try to subsctract two dates

[Martin_Leclercq]

Hello everybody
I’m a teacher and i would use airtable to manage my schedule
My teaching lesson start the 8/9/2018 8:45 and finish at 8/9/2018 at 12h i try two substract those to have the during time of my lesson.
Could you help me ?
thanks a lot
Martin

[Martin_Leclercq]

Oh that’s ok i found it’s
DATETIME_DIFF({end}, {start}, ‘seconds’)
my post is useless how i can delete it ?