Hours which are past midnight are suffixed with next day date. In Panchang day starts and ends with sunrise.
Mithuna Sankranti marks the beginning of the third Solar month in Hindu calendar. All twelve Sankranti(s) in the year are highly auspicious for Dan-Punya activities. Only certain time duration before or after each Sankranti moment is considered auspicious for Sankranti related activities.
For Mithuna Sankranti sixteen Ghati(s) after the Sankranti moment are considered Shubh or auspicious and the time window from Sankranti to sixteen Ghati after Sankranti is taken for all Dan-Punya activities.
During Mithuna Sankranti gifting or donating clothes is considered highly auspicious.
Currently Mithuna Sankranti falls on 14th June or on 15th June. In South India Sankranti is called as Sankramanam.