Remembering birthdays or other personal holidays can be difficult without use of a calendar or date book. If you're already using Gmail and Google Calendar these dates can kept on hand at all times. To take the pressure off yourself to remember important dates, just follow these steps:
1. Log into Gmail and choose Contacts from the menu in the upper left corner. It will look something like this:

2. Add birthdays to your individual contacts that the calendar will be able to use. Save the contact info and then open Google Calendar.
3. Save the contact and then go to Google Calendar.
4. In the Other Calendars box to the lower left, click on Add, and then Browse Interesting Calendars.
5. Choose the More tab near the top of this area, and then click Subscribe next to Contacts' birthdays and events.
6. Go back to the main calendar page. Click on Birthdays so that the calendar name is highlighted, which will allow these dates to show on your main calendar.
7. Set a color for these dates by clicking the drop down arrow to the right of Birthdays, to help differentiate them from other events in your calendar.
This contact calendar can also be used for anniversaries and other custom dates.