Is the prayer invalidated if the time passes while it was still being established?
Scholars have consensus on the view that prayer is not invalidated if prayer time ends while it is being established, except fajr and Friday prayers. Imam Abu Hanifa, based on the hadiths which prohibit establishing prayer when the sun rises, says that sunrise invalidates the prayer that is being established. On the other hand, Imam Abu Yusuf and Muhamamd expressed that prayer will not be invalidated if one sits for a duration enough at least to recite tashahhud in the last sitting (Kasani, Bada’i, I, 124; Ibn al-Humam, Fath, I, 397). Other jurisprudential schools express that prayer is not invalidated if it is being established when the prayer time ends by taking as reference the hadith (Bukhari, Mawaqit, 27) of Prophet Muhammad (saw) saying that prayer may be completed and will be valid if sun rises after its one rakat is established or sun sets after one rakat of ‘asr prayer is established (Ibn Rushd, Bidayah, I, 95; Ibn Qudamah, al-Mughni, II, 16-17).
Accordingly, although there is a conflict about fajr prayer, the prayer that is being established when the next prayer time starts is not nullified.
Source: Presidency Of Religious Affairs The Turkey, High Board of Religious Affairs FATWAS