Your roaming validity starts once you connect to the local network in the country you’ve travelled to. Don’t worry; it won’t start when you make a purchase before travelling.
If you purchased daily calls or data, they will run out 24 hours from the time you start using. You might consume all your daily roaming calls or data before the day ends.
If you purchased weekly calls or data, you will have 7 days from the time you start using or until you’ve consumed them all.