Time control of signal generation

[SpongeBobaa]

From the update of the ephemeris, it can be seen that the ephemeris data is updated every two hours.

I use a receiver to receive ephemeris data. The ephemeris time received from 00:00 to 01:59 is 00:00, and the ephemeris time received from 02:00 to 03:59 is 02:00.

I want to generate real-time GPS spoofing signals using the ephemeris data I receive.

Why do I try to use the 00:00 ephemeris data to generate signals, but cannot generate signals within the time interval of 00:00-01:59.