5th September 1964, ??:??:?? (UTC), somewhere in Romania: Under unusual daylight, delicate leaves rustle lightly, revealing bright autumn skies - Bob's set is reversed. (B > b)
How does that sum to 44396175618?
Birthday Hint:
[Unix Timestamp] + [11-digit number] + [7-digit number].
I think it's best to focus on the first two, if you get them correct the last will reveal itself anyway.
Note: The mathematics is only here because it is recommended to use it with the calculation-puzzle tag. No deeper mathematical knowledge is required.