middle of the Sun's disk becomes visible at eastern horizon.
But the above ignores refraction. Due to refraction Sun becomes visible even when it is below eastern horizon. Hindu Sunrise = Astronomical Sunrise + Time taken by Sun to rise half of its diameter+ Time taken by Sun to rise further to neutralize refraction effect.
The actual time when Sun rises in the morning is 'Sunrise time' and the actual time when Sun sets in the evening is 'Sunset time'. In Panchang, Sunrise and sunset timings are very significant for calculating the important times of the day.
With Sun rise the day begins. It is believed that initiating work or activating with begin of day is very blessed and fresh. At the beginning of the day with sunrise, and at the beginning of evening with sunset, Aarti, pooja is offered to delight God in India. If you also offer your worship during these timings you will be blessed with happiness and peace in life.Get the actual sunrise /sunset timing here...