Can repeated call-signs be present in one day? I am working with a big ADS-B traffic sample of one day Europe, and identified repeated call signs. Examples include:


Flight that ends in an airport and repeated call sign starts from there.
Two flights with the same call sign, ADEP and ADES.
Four Different ADEP and ADES.


I thought in one day it was not possible to have repeated call signs.
Is this possible? Is my data wrong?
It is no problem to have the same call sign on the same day. As long as the same call sign is not uses at the same time there is no problem. 

For VFR flights, the same call sign can even be used at the same time as long as it is not in the same airspace. 

Many of the ADS-B duplicated call signs on a single are aircraft registrations coded in the transponder's aircraft ID field, typically from General Aviation flights