Add to my phone’s calendar subscribes your phone to the 5G division’s games. They appear in your own calendar app and keep themselves up to date: a game moved or cancelled on this website changes on your phone within a few hours.

iPhone: tap the button and choose Subscribe. If nothing happens, copy this address and go to Settings › Apps › Calendar › Calendar Accounts › Add Account › Other › Add Subscribed Calendar:
https://ctbball.org/schedule.ics?pool=5G

Android / Google Calendar: on a computer open calendar.google.com, find Other calendars on the left, press +, choose From URL, and paste the address above. It then appears on your phone too.

Download (.ics) saves the games once, as they are today. It will not follow later changes.