How far in advance can I get reminders for the upcoming birthdays?

You will get reminders for upcoming birthdays for a maximum of 14 days in advance and a minimum of 1 day in advance.  You also have the option to get a reminder on the date of the birthday.
 
However, by default, we will send you the reminder 7 days in advance and also on the date of the birthday.

You can change your Birthday Reminder Settings, as per your convenience.