Question:
When should a fasting person in a skyscraper break their fast if the sun is visible and timetable shows different time?

Answer:

In the Name of Allah, the Most Gracious, the Most Merciful.

As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.

The Qur’ān has explicitly stated the end time of fasting.  Allah Ta’ālā states:
“And eat and drink until the white thread of dawn becomes distinct to you from the black thread [of night]. Then complete the fast until the sunset.” (Qur’ān 2:187)

The ‘aḥādīth have explicit mention of sunset being the end time of fasting.  The Prophet ﷺ said,
“When night falls from this side and the day vanishes from this side and the sun sets, then the fasting person should break his fast.” (ṣaḥīḥ al-Bukhārī 30:61)[1]

Imam al-Ṭaḥṭāwī raḥimahullah (d.1231AH) quoting Khulāṣah al-Fatāwā states:

“A person who has ascended the minaret in Alexandria cannot break the fast if the sun is still visible to him in the horizon, even though, those on the ground in Alexandria will be breaking the fast since the sun has disappeared from them.”[2]

Hence, those residing in high altitudes must exercise caution if the sun is visible to them in the horizon.  They must break the fast either after physically seeing the sun set below the horizon or after they firmly presume that the sun has now set despite not seeing in set.[3]  Waiting a couple of minutes more than the prescribed time on the timetable will suffice.

And Allah Ta’ālā Alone Knows Best
Mufti Faraz Adam,
www.darulfiqh.com