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1.
The jetlag-like disruption of your circadian rhythms that occurs on the Monday after Daylight Saving Time comes into effect.
"Sorry I'm late. I've got the goddamn DST-lag. It took three cups of coffee before I could wake up enough to leave the house."
by Adman12 April 03, 2006
 
2.
the sleepy feeling you get when trying to adjust to the new time for daylight saving time
chris: man i feel so tired

jim: why? what'd you do yesterday?

chris: nothing, i just got a little DST lag
by J-SLIK November 06, 2007