All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The matters that pertain to work, like attendance and so forth, depend on what is agreed upon in the contract and other work rules. So a worker is obliged to abide by what he has agreed upon.
Allaah Says (what means): {O you who believe! Fulfil your obligations.} [Quran 5:1] Moreover, the Prophet said: "The Muslims should fulfil their conditions within what is permissible." [Abu Daawood]
So if a worker comes later than the time that is agreed upon without any excuse or permission by the institution [for which he works], then he is sinful.
Imaam An-Nawawi reported that there is a consensus amongst the scholars that whoever promises a person something that is not forbidden, he has to fulfil his promise. However, the scholars differed about the ruling of fulfilling a promise, whether it is an obligation or something desirable. The most preponderant opinion; however, is that if the promise of a person to someone else makes the latter involved in some obligations and expenses then it becomes an obligation to fulfil the promise but if the promise does not cause him any expenses or indulge him in some other liabilities, then it is desirable to fulfil it.
Finally, it should be noted that promising someone to do something without any intention to fulfil it, is a characteristic of hypocrites. The Prophet when speaking about the characteristics of hypocrites, he said: "…If he promises he breaks his promise…" [Al-Bukhari and Muslim]
Allaah Knows best.