Result of Time Calculation Is Not Correct

It is considered that you did not specify the time in seconds.
When performing time calculation, you need to specify the time in seconds. Enter "3600 seconds" when specifying 1 hour.
Calculation of 1 day is "60 (seconds) * 60 (minutes) * 24 (hours)".

For example, if you want to calculate the date that is 7 days before the Date field of which field code is "A", you set a formula as follows in the Calculated field.

A-(7*60*60*24)