When Does the TV Show "Smallville" Season Three (2003) Take Place?
"Smallville" season three is a superhero television series showran by Alfred Gough with Miles Millar [adapting "?" #? (YEAR) by ?] that premiered October 1st, 2003. So when is "Smallville" season 3 set?
It takes place on an alternate timeline of the fictional DC Films Universe in the years:
We know this because the very first shot of season three episode one "Exile" includes a time setting white-on-black subtitle reading "Three Months Later" all but confirming this season begins 3 months after the previous season ends.

2003 AD - 2004 AD
We know this because the very first shot of season three episode one "Exile" includes a time setting white-on-black subtitle reading "Three Months Later" all but confirming this season begins 3 months after the previous season ends.
Also, the next season's premiere, season four episode one "Crusade" (2004), opens with a time setting white-on-black title card reading "Three Months Later" and that season takes place in 2004 AD. So this season must also take place partially during or before 2004 AD.
Later, during the third season's finale season three episode twenty-two "Covenant" (2004), when Clark Kent/Kal-El is confronted with someone claiming to be Kara from planet Krypton, he asks, "Why don't you start by telling me where you've been for the past 14 years?" and in the very next scene he says, "You've been down here ever since the meteor shower?", which was seen in the prologue of season one episode one "Pilot" (2001) and takes place in October of 1989 AD.
1,989 + 14 = 2,003.
It is the third-earliest chronological TV series in the DC Films Universe timeline (a chronological first to feature Kal-El/Clark Kent/Superman) and can be watched either at its timeline point or entirely separately.

