Date type handling code has problems

[beastd]

This seems not maintained anymore, but maybe this helps people noticing problems.

• The date writing code, writes the timestamp with offset zero (UTC) and after that writes the current timezone offset.
• The date reading code, reads the timestamp and then adds the stored offset and subtracts current timezone offset.

The reading code will lead to wrong results when the timezone written is different from the current timezone and if it's the same it will be a no-op.

Regarding the writing code, i guess it should maybe just write zero for the timezone. At least that is what I found written in the Adobe AMF 0 spec.