Hi @Anonymous
This is the expression to parse the string to ISO 8601 format (yyyy-MM-ddThh:mm:ssZ): formatDateTime('January 22, 2020 9:21 PM','yyyy-MM-ddTHH:mm:ssZ')
You can then add required minutes to the datetime value: addMinutes(formatDateTime('January 22, 2020 9:21 PM','yyyy-MM-ddTHH:mm:ssZ'),-30)
Example using the above expressions with the Compose action:

Ref date comparison... it's a little hard to advise as I don't follow your logic, it's impossible for a value to be equal to itself minus a value?!? 🙂
I'm guessing you would compare against another datetime value or the current time (utcNow())...
HTH
Jay
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