Namaskaram,
If you are looking for timings here are the general guidelines:
Nakshatra jyotir Arabhya sUryasyOdaya darshanAt prAtaH sandhyeti tam prAhuH shrutayO muni sattamA
During the morning, the time from the visibility of the stars to the time of first appearance of the sun in the sky is considered as pratah sandhya time.
Sama sUryE tu madhyAhnE
When the sun is exactly on the top that is the primary time for madhyAhnE sandhya
atyartha yAmAt Saayaam sandhyA mAdhyAhnikI matA
If you divide the time from sunrise to sunset into half, the second half is the gauna kala for marhyanika sandhya
arthAstamita kAlAt yaH sandhiH AtArakOdayAt tatra sandhyAm upAsIta sAyamkAle samAhitaH
From the time the sun has half set to the time starts start appearing in the sky in the night is the mukhya Kalam for saayaam sandhya
That said, as shri satyam ji said below, I have also personally found the app called Drik panchang (from which the screenshot is) pretty accurate for determining daily sandhya times.
Kind regards,
Raghav Karumur