You can add your contact's birthdays as an additional calendar in your Google calendar via their web interface. DigiCal will then display all your contact's birthdays accordingly.
Adding contacts' Birthdays to your Google Calendar
Google Calendar lets you add yearly recurring events; handy to see friends' birthdays in advance, for example. Additionally, Gmail lets you add dates to your contacts; handy to note friends' birthdays.
Conveniently, Google Calendar can automatically pick up birthdays you've added to your Gmail contacts and show them as a special schedule of all-day events — even including birthday cakes icons!
Add Your Gmail Contacts' Birthdays to Google Calendar
- Go to the Google Calendar page: Click on the cogwheel button on the top right hand side and select Settings.
- Go to the "Calendar" tab
- Click on "Browse interesting calendars" in the other calenders section
- Go to the "More" tab
- There's a calendar called "contact's birthdays and events", click on subscribe
*Note that you cannot add notifications — for instance by email or SMS — to your Google Calendar birthday calendar. You can get an RSS feed of upcoming birthdays, though.
Therefore, if you would like to get alerts, you can also copy individual birthdays to a personal calendar (open the event and select copy to my calendar).
If you don't see the new calendar please make sure it's set to sync and set to display: https://digibites.zendesk.com/hc/en-us/articles/200299933-How-do-I-select-which-calendars-to-display-