Star Trek: Enterprise and
Star Trek: Voyager are currently in syndication. That means that the shows are available for local television stations or station groups. These stations can choose which episodes to air and the day and time in which to air them.
The original Star Trek series now airs on G4 and we can tell you when it will air on that network. But with a syndicated show like Enterprise, we can only tell you when it's on if you tell us where you live.
To find out if and when Enterprise or Voyager is playing in your area, follow the instructions here.