It usually takes a couple of cycles for them to become normal again.
also, before my d&c my cycles were usually 24 days apart, maybe a few times 25 days.. since the d&c i had what i assumed was my first period in april, then 30 days later another period, then 25 days later another, then more bleeding 4 days after that one.. it's been crazy.
i think it depends a lot on what you had your d&c for.
i had a d&c because i had a molar pregnancy, that was in february. i didn't get a period until april, but ever since then they have been irregular.
After I had a d&c I got my period 5 weeks from the date of the d&c, and it was heavier than normal however I was on the pill before I concieved. It seemed to last a couple days longer as well. They came regularly for the next 3 months give or take a couple of days, but with still the same heaviness and lasting a little longer prior to the d&c. After my third cycle I conceived again. =)