The checks on the Gaia satellite are proceeding nominally, enabling Arianespace in agreement with ESA to announce the launch date.
Liftoff of the Soyuz ST-B launcher is set for Thursday, December 19, at precisely:
09:12:18 am (UTC)
06:12:18 am (local time in French Guiana)
10:12:18 am (Paris)
04:12:18 am (Washington, D.C.)
12:12:18 pm (Moscow)