Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
First of all, we ask Allah to reward your father for being keen on performing the prayer at its fixed time. Prayers are important. They are a relationship between a servant and his Lord.
It is the prayer that distinguishes a Muslim from a Kafir (non-Muslim), it is the first thing a person will be accounted for on the Day of Judgment.
Our advice is that you should advice your father to perform the prayer at their fixed time as it is a great sin to delay prayers without a sound valid reason.
Allah says: "Then, there has succeeded them a posterity who have given up As-Salât (the prayers) [i.e. made their Salât (prayers) to be lost, either by not offering them or by not offering them perfectly or by not offering them in their proper fixed times, etc.] and have followed lusts. So they will be thrown in Hell. (Maryam 19:59)
Your father has to convince his boss to let him pray on time. If his request is granted, Alhamdulillah (Praise be to Allah). But if his boss does not accept, then your father has to leave this job. There is no good in a job that leads to not performing prayers on time.
May Allah facilitate for him a better job.
Whoever abandons something for the sake of Allah, Allah will recompense him with something better.
Allah also says: "And whosoever fears Allâh and keeps his duty to Him, He will make a way for him to get out (from every difficulty). And He will provide him from (sources) he never could imagine." (At-Talaq 65:2-3)
He has also to repent to Allah for not praying on time in the past.
Allah knows best.