Is Calendar Mutable - What The Value Was Initialized With

I have a field that initializes a Calendar object:

Java Code:

private Calendar zeroPointTime = zeroPointTime();
private Calendar zeroPointTime(){
int year = 2000;
int month = 0;
int date = 1;
int hourOfDay = 0;
int minute = 0;
Calendar calendarTime = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
calendarTime.set(year, month, date, hourOfDay, minute);

[Code] ....

But other times I need to reference what the value was initialized with, not offset values added to it with various function calls.

When I use add() will that modify zeroPointTime? If so, how can I add seconds to a Calendar object without altering its value?