This python script securely connects to your Google Calendar and computes future accrued biweekly vacation hours.
Follow the instruction on this site to set up you Google API Authorization: https://developers.google.com/api-client-library/python/start/get_started
Modify the configuration file with you vacation days per year that will accrue and the start and end date you'd like to run the script.
On the start day you chose, make an all-day event name "Vacation Hours: ". The script uses this info as the starting point.
Any day which you'll be taking as vacation label with "Vacation Day" or "Half Vacation Day" and the script will either subtract 8 or 4 hours from the accrual, respectively.
Then just run the script!