Freeciv

The field convert_time is for the convert activity, not for upgrade.

Yes, I'm talking about a conversion, convert_time 3 had no effect. The idea was to convert galleons to arguably better frigates, keeping "caravel obsoleted by galleon" as is (in classic, etc.). When that didn't work as expected I switched it to "caravel obsoleted by frigate" and a "downgrade" conversion frigate to galleon in one turn.

Likely 'convert_time' is in movement points, not an actual number of turns. (This is to guess reason for the behavior you see, not to claim it's correct)

Okay, info added to http://freeciv.wikia.com/wiki/How_to_update_a_ruleset_from_2.4_to_2.5#Unit_conversion

Please check if that's correct, I haven't tested it, and I'm not sure about "rounded up" (apart from "convert_time 1 takes one turn no matter what the move rate is".)

Various "speed is multiplied by ACTIVITY_COUNT" comments in common/unit.c apparently should say ACTIVITY_FACTOR instead to get a factor 10 on both sides of the ACTIVITY_CONVERT case in server/unittools.c

I'm no longer sure if the code should be changed, or current behavior documented better. Looking my original use-cases it seems current behavior is intentional.

Arguments for keeping current behavior:
1) Consistency with other activity time (in terrain.ruleset) definitions
2) Possibility to adjust the conversion time based on veterancy. Veteran "Cannon crew" can set up "Cannon" faster than regular.