The orignal .5 years to completioin was assuming that the number of research points assigned to it stayed constant for the next 5 turns. The research point production of your colonies is affected by happiness, so one of your planets dropped a bit in happiness and that lowered your overall research generation, which caused the project completion to be pushed back a turn.
EDIT: Or possibly you gave a colony ship orders and it drew enough population from your homewolrd to have the same effect. That also has an effect on research production.
EDIT2: Of course, I am making the assumption that you didn't do anythign silly like scrap a research faciliity that turn, or that no alien invaders or asteroid strikes took one away from you.
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Basically anything that could cause your research production to drop could cause the occurance you saw here, because you research levels have to stay constant fo rthat number to be correct. ON the other hand a jump in research production could have the opposite effect. You could go from .5 turns to .3 turns in one turn. But the human mind being what it is we tend to ignore unexpected blessings like that and only notice the negatives.
Geoschmo
[ August 12, 2002, 18:47: Message edited by: geoschmo ]