The angels had a charge and 'ways to walk in'. Some at least had a delegated administration from God to fulfill, and that with accountability. The fact that they sinned proves a law existed for them because sins are only counted with regard to law(s) broken. Well known is the story of Lucifer's revealed inner iniquity that eventually motivated him to mount a foolish attack on the highest throne of heaven. Only pride could blind anyone to that extent, to the possibility of success of such a venture.
Further examples of periods of time in Scripture of various lengths: Exa. 16). Da 12:1 [And at that time shall Michael stand up ... and there shall be a time of trouble, such as never was since there was a nation even to that same time: and at that time thy people shall be delivered]. Here is a specific time for a specific event in a period of time resulting in a 'deliverance' time. Exa. 17). Da 12:4 [seal the book, even to the time of the end]. Exa. 18). Da 12:7 [time, times, and an half; and when he shall have accomplished to scatter the power of the holy people, all these things shall be finished]. 1 + 2 + 1/2 = 3.5 years (known by comparing passages that use 42 months). Notice this is the 'accomplishment' time, and then the 'things finished' time. Exa. 19). Da 12:9 [the words are closed up and sealed till the time of the end]. Exa. 20). Da 12:11 And from the time that the daily sacrifice shall be taken away, and the abomination that maketh desolate set up, there shall be a thousand two hundred and ninety days. One time of 1,290 days, and 1,290 specific 24 hr. days in sequence; which in turn still refer to the 3.5 years (time, times, and half time) and the 42 months.
What was God after in all that happened with the angelic orders of the past? It was He that put in place the test, and the opportunity for those whom he had created to prove themselves. An opportunity for them to show loyalty, faithfulness, and thankfulness in order to qualify themselves for eternal tasks and quests. Certainly if you were to invent something, you would run it through a series of tests to see if it fulfilled your purpose? However, God has added one level of testing more than that of a simple invention because, His set of tests gives opportunity to the living invention prove itself!
... all to the glory of God!