How to make a Boolean variable true in an exact minute X day ago?

Question

Here's a Boolean value, it's perfect for today:

myTimeStamp = hour(time, 'GMT-5') == 9 and minute(time, 'GMT-5') == 30

I want it to be true not today but dayOffset days earlier.

For example, if dayOffset = 1, then

• let's say it's 28 February 09:31 AM, thus myTimeStamp was true on 27 February 9:30.
• BUT as a day goes by, and now it's 1 March 09:31, myTimeStamp gets true on 28 February 09:30 (stepping 1 day), no longer marking 09:30 on 27 February.