IF statement to Convert TZ before and after time change

IF statement to Convert TZ before and after time change

Hello! 

Background: I use "convert_tz("last_received_at", '+00:00', '-05:00')" in a formula column to adjust a date from UTC into Eastern time. After the recent time change for Eastern, I need this formula to continue to adjust for -05:00 before March 14 at 1:59 AM and adjust for -4:00 after that date.

Request: Looking for help me writing an IF statement like this: IF "last_received_at" before March 14 at 1:59 AM, convert_tz("last_received_at", '+00:00', '-05:00') and if "last_received_at" after March 14 at 1:59 AM, convert_tz("last_received_at", '+00:00', '-04:00')

 Here is the date format that I use for the "last_received_at" column: yyyy-MM-dd HH:mm:ss z