1.3 Time.
Time is measured in frames, with one unit of Game-Time (GT) equal to 50 frames of animation in fast mode, and 25 frames in slow mode. Most time-units in the game are measured in frames, including build time, rate of attack and rate of movement. All GT measurements listed within this site are based on fast-mode, so one diplomatic center unit will train in one Game-Time second (50 frames).
1.3.1 Construction Time.

The construction times listed in this database represent the time it takes to construct a building with 10 peasants. This time can only be attained by assigning 10 peasants to the construction. When fewer than 10 peasants are assigned, the increase in construction time can be quite dramatic however the construction time can never be longer than 10x that obtained with 10 peasants. To predict how long it will take to construct a building, use the following formula:

actual_time = 10 / num_peasants * db_time / 50 frames per second

For example, an English tower can be constructed in 90 GT with 10 peasants. We know from experience that it is only possible to put 9 peasants on a tower, so a buildtime of (4500/50) 90 GT can never actually be attained:

When more than 10 peasants are assigned to the building's construction, the construction time will be faster, for example, the English Academy (with a construction time listed at 2000, or 40 GT): 
The more peasants the better. Generally speaking, 20 peasants will reduce the construction time by half, 30 by 67%, 40 by 75%, etc. No buildings in the game allow more than 40 peasants (the average is somewhere around 24), and the actual number allowed varies from building to building. The max number of peasants allowed to construct each building is presented next to the build time.

Yes there is always an exception to the rule. Russian peasants actually build slower than all the rest. Use the following formula to determine how long it will take a Russian peasant to construct a building:

actual_time = 14 / num_peasants * db_time / 50 frames per second

So, to achieve listed construction times, 14 Russian peasants are needed. To reduce the construction time of a Russian building by half, 28 Russian peasants are needed.
1.3.2 Construction time points of interest.
I feel like it would be a good idea to highlight a few points of interest here. While this sort of information does not necessarily affect the overall balance of the game, it can be useful to know.

ยท         Markets:

- Nations using the Spanish or Ukrainian style market can build the fastest, in 5 GT: Piemonte, Portugal, Spain, Ukraine, Venice. So for an early trade this might be an  important advantage for certain settings (like 5000 games).
- Nations using the Austrian style market come next, at 6 GT: Austria, Bavaria, Denmark, England, France, Poland, Prussia, Netherlands, Saxony, Sweden.
- The Russian market comes next, at 12 GT. Slow, eh?
- Nations using the Algerian style market build the slowest (17 GT): Algeria & Turkey. They only use 9 peasants (you can manually assign a 10th builder to bring the time down to 15 GT if you are desperate), so these guys have no chance of getting an early market under any start.

  • Academies: From best (13 GT) to worst (22 GT): Spain, Bavaria, Piemonte, Austria, Saxony, France, Prussia, England, Portugal, Sweden, Poland, Venice, , Turkey/Algeria, Denmark, Netherlands (18), and Russia (22). Ukraine, the exception, can build an academy in under 1 GT (that's not a typo).
  • Diplomatic Centers: From best (7 GT) to worst (10 GT): Austria, Portugal, Denmark, Spain, Ukraine, Piemonte, Saxony, Prussia, Poland, Venice, Russia, Netherlands, Bavaria, England, Sweden and France. Turkey and Algeria come in last at 15 GT.
  • Shipyards: Turkey & Algeria can afford 28 peasants (36/9 GT), followed by Portugal with 27 peasants (38/10 GT), Ukraine peasants 25 (40/10 GT) and everybody else with 24 peasants (42/11 GT). Russia, with 37 slow-building peasants can erect a shipyard in (39/10) GT.
  • Towers: Turkey and Algeria can put 14 peasants on their towers. All other nations are limited to 9. These guys already build a tower fast, so this actually means a Turkish or Algerian tower can go up in as little as 50 GT, while the quickest anybody else can put one up is 100 GT. With 14 peasants, a Russian tower can be built in 70 GT (remember, Russian peasants build slower).
  • Turkey and Algeria: For all other buildings, they have the lowest numbers of peasants available to construct buildings, often 50% fewer.