Set in an age where space travel is fairly commonplace, colonies outside the protagonist's home planet have already been set (or are being set right at the moment) and there's interplanetary commerce and possibly even tourism going on.
Alternate names: Spacefarer era
Name variations: spacefaring era, spacefarer age
The first video game about Spacefaring age was released in 1971.
Extraterrestrial, space, spacecraft and spacestation tags imply this, but are not reliable indicators. The game can be set on Earth or nearby planet that does not require spacefaring age, the setting can be completely fictional one where determining this is otherwise impossible.
There is seemingly no actual name for this age agreed upon yet.
As some examples that would seem to be in this but actually are not:
* Dominant Species -- has humans in some far away world, but you're not playing as humans, but rather the local natives.
* UFO: Afterlight -- humans were transported to mars by aliens, and lack the technology themselves to do the same.
* Moonbase Alpha -- the moonbase is purely scientific station and no space travel is done for other reasons.
.. and anything with early space age, where space travel is limited for mainly research (as it is/was in 20th and 21st century).
As other examples, games that would seem NOT to be this but are:
* Wizardry 8
This is NOT for space age.