Mixpanel is built to allow you to deliver messages to users at the perfect time. Send in custom date Properties to deliver messages to users based on a past date, like users who recently signed up:
Or based on a specific future date, like an upcoming wedding date or when a customer is up for renewal:
Birthdays and anniversaries
If the date on which you’d like to target was in the past (like a birthday or an anniversary), targeting is a bit tricker. For example, if you have a user’s birthday stored as May 25, 1986 and then use “Birthday will occur within four weeks,” they will never be targeted with this message since we are not four weeks away from May 25, 1986.
Set a property called something like “Birthday Month.” Then, set up 12 different email messages where the targeting is each month. For example, "Send a message on December 31 to all users whose Birthday Month contains January."
Export your people profiles to CSV, change all the birthday properties to have the current year, and re-import as a new property (so that profiles also contain the original data with the real birth year), which will then allow the “will occur within” targeting to work properly with the new property. This is a bit cumbersome because it will have to be done annually to update the birthday year to the current year.