Converting a birthdate into milliseconds

How do I take a birthdate entered by a user and turn into milliseconds so that I can calculate how old they would be on a different planet

Here is the code I have so far:

DateFormat df = new SimpleDateFormat("MM dd yyyy");
Date dateBirth = df.parse(birthdate);
Calendar calBirth = new GregorianCalendar();
calBirth.setTime(dateBirth);

Edit 1: Yes I'm looking to get the milliseconds between the user's birthdate and the current time in order to di开发者_StackOverflow社区vide that by a planet's days in a year

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dateBirth.getTime() will give you the number of milliseconds since the epoch, if that's what you're looking for?

EDIT -

In order to get the difference between now and the birthday, you can obviously just get now as a Date object, convert that to milliseconds, and subtract - eg now.GetTime() - dateBirth.GetTime().

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Date d = new Date();
long msSinceBirth = d.getTime() - dateBirth.getTime();

This assumes the user is born in the past. Time travellers will produce negative values for msSinceBirth.

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Not quite sure I fully understand the question, but Calendar has the method right in it...

getTimeInMillis

public long getTimeInMillis()

Gets this Calendar's current time as a long.

Returns: the current time as UTC milliseconds from the epoch.

See Also: getTime(), setTimeInMillis(long)