Sankashti Chaturthi is decided at moonrise
Sankashti Chaturthi is observed according to the chaturthi present at local moonrise.
A daily panchangam usually lists the tithi at sunrise. Sankashti uses a different reference point: moonrise at the place of observance.
The rule
Sankashti takes the chaturthi present at moonrise. This corresponds to the practice of breaking the fast after sighting the Moon.
Why the listed dates may differ
A chaturthi can begin after sunrise and still be present at moonrise that evening. It may then be listed as the sunrise tithi on the following civil date. A sunrise tithi list and a Sankashti date list can therefore show different dates for the same tithi.
Why the location matters
Moonrise varies by location. When a tithi boundary falls close to moonrise, the observance date may differ between places. Check the city as well as the date when comparing calendars.