Riddles I Couldn't Resist

After checking a fellow blogger's page (see link in post above), I had to share these riddles found there. I answered both quickly, but I still think they're fun!

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I'm double, I'm single,
I'm black blue and grey,
I'm read from both ends,
And the same either way.

Something very extraordinary happened on the 6th of May, 1978 at 12:34 a.m. What was it?