The duration of your data package starts as soon as your Travel eSIM connects to a network at your destination for the first time. From that point, you have 7 days for 1 GB data packages and 30 days for all other data packages to use your data volume.
You can see the exact duration and your remaining data volume any time in your Cockpit under «Travel eSIM».
Good to know: once your data package is activated, the duration keeps running – even if you switch the eSIM off in between or don't use any data. So only activate your data package when you really need it.