How does Civ 5 "progress"?

I just downloaded Civ 5, and I saw many videos about it. Im wondering if Civ 5 starts in some very old time, and then progresses to more and more advanced state, if it does work like that, can you get to the 20th century?

Yes, the games starts in 4000 BC (assuming you don't select a later era start) and, unless you disable time victory, will end in 2050. The number of years covered by a single turn declines as the game progresses. At Standard speed the years/turn increments are as follows:

40 Years per turn, 4000 BC until 1000 BC (turns 0-75)
25 Years per turn, until 500 AD (turns 76-135)
20 Years per turn, until 1000 AD (turns 136-160)
10 Years per turn, until 1500 AD (turns 160-210)
5 Years per turn, until 1800 AD (turns 211-270)
2 Years per turn, until 1900 AD (turns 271-320)
1 Year per turn, until 2020 AD (turns 321-440)
6 Months per turn, until 2050 AD (turns 441-500)

Browd is correct on the time scale at standard speed.

With BNW, most victories occur between 1850 & 1950 AD though.

Marathon:
15 years per turn, 4000 BC until 2500 BC (turns 0 - 100)
10 years per turn, until 500 AD (turns 101-400)
5 years per turn, until 1350 AD (turns 401-570)
2 years per turn, until 1752 AD (turns 571-771)
1 year per turn, until 1881 AD (turns 771-900)
6 months per turn, until 1971 AD (turns 901-1080)
3 months per turn, until 2037 AD (turns 1081-1344)
1 month per turn, until 2050 AD (turns 1345-1500)

Epic:
25 years per turn, 4000 BC until 500 BC (turns 0-140)
15 years per turn, until 850 AD (turns 141-230)
10 years per turn, until 1250 AD (turns 231-270)
5 years per turn, until 1700 AD (turns 271-360)
2 years per turn, until 1840 AD (turns 361-430)
1 year per turn, until 1940 AD (turns 431-530)
6 months per turn, until 2050 AD (turns 531-750)

Quick:
60 years per turn, 4000 BC until 1000 BC (turns 0-50)
40 years per turn, until 200 AD (turns 51-80)
30 years per turn, until 800 AD (turns 81-100)
20 years per turn, until 1400 AD (turns 101-130)
10 years per turn, until 1650 AD (turns 131-155)
5 years per turn, until 1850 AD (turns 156-195)
2 years per turn, until 1980 AD (turns 196-260)
1 year per turn, until 2050 AD (turns 261-330)