Currently Subscribe to Team Calendars from Google Calendar documentation states a 3 to 24-hour sync delay time window:

Known issues and limitations

These limitations are due to different issues in Google Calendar.

• Google Calendar refresh times are delayed. They range from 3 hours to 24 hours.
• Subscriptions are read-only (you cannot modify events from Google Calendar).
• Subscribed Team Calendar's names are truncated if they have a space in the title.

However, many organizations need updates pushed from Team Calendar to Google Calendar faster than 3-24 hours. Having a feature to customize the sync time OR even a consistent time frame would offer a better experience.