Time limit on D-Visa ?

Is there a time limit on a D-Visa that after it is issued and the time you enter BG ? ie  I get my D-visa and have to what a couple months before leaving the US.

A single entry visa (most D type visas are single entry) expires 3 months after date of issue.

http://www.bulgaria-embassy.org/bg/ko-was-uslugi/vizi/

OK Thanks

The C visa is for 3 months and the D visa is for 6 months

That's what our friends got

The D visa is good for either 6 months or 12 months AFTER entering. But it must be used to enter within 3 months of issue.