Answers from TW Forum (maybe I'm not the only one noob, who didn't know how to do it and someone will find this theme useful):
Docm30:
Make a simple trigger that fires once every 24 hours and adds 1 to your day variable and then check once a day for the variable reaching certain days.
kalarhanstore_current_day = 2272 # (store_current_day, <destination>),
# Stores number of days that have passed since beginning of the game. Commonly used to track time when high accuracy is not required
Docm30Oh yeah. It's the weather you can't read, not the date.