I forgot the time difference.

我忘了时差。

Compute the time difference.

计算时间差。

I forgot about the time difference.

我都忘了时差的问题了。。

Your means that there is no time difference!

你的意思是说这竟没有时差！

Please tell me the time difference and the charge.

请告诉我时差以及费用。