The Google Maps Help says:
How old is the satellite map data on Google Maps?
Google Maps uses the same satellite data as Google Earth. Google Earth
acquires the best imagery available, most of which is approximately one
to three years old.
We strive to update our data regularly. Unfortunately, we're not able to
provide you with detailed information regarding when a specific area
will be updated. Also, we do not offer high resolution data by order as
this information will be added when it is available from our data
providers.