English Explanation of Mishnah Bava Metzia 9:11

One that is hired during the day collects his wages all during [the ensuing] night. One that is hired during the night collects his wages all during [the ensuing] day.
One that is hired by the hour collects his wages all during [the ensuing] day or [the ensuing] night.
If one was hired by the week, or by the month, or by the year, or by the week of years, if his time of hire expired during the day, he collects his wages all during [the ensuing] day. If his time of hire expired during the night, he collects his wages all during [the ensuing] day and night.
Deuteronomy 24:14-15 and Leviticus 19:13, both command that a worker’s wages must be paid on the same day, before the sun sets. These verses deal directly with one who works during the day, presumably on a daily wage. Mishnah eleven deals with workers who work at night, and with workers who work on hourly, weekly, monthly or yearly wages. Mishnah twelve deals with other laws concerning the commandment not to delay a worker’s wages and its applicability.
The general rule of our mishnah is that an employer may pay his employee within one time period of either day or night from the time of the completion of the work. He may not withhold the wages any longer. If the work was done during the day the employer may pay his employee at any time during the ensuing night. If he were to wait until the following morning he would be violating the commandment not to delay payment. If the work was done during the night he has until the end of the ensuing day to pay the employee.
If the employee was hired on an hourly basis the same rule still basically applies: the employer has one time period from the time of the completion of the work to pay the employee, whether that time period is the day or the night.
Similarly, if the employee is hired on a long term basis, for instance a week, a month, a year or even seven years, and it was agreed that the salary would be paid only upon completion of the work, the employer basically has one time period after the completion to pay his employee. The one exception is if the work is completed at night. According to section three of our mishnah, in such a case he has two time periods: the entire day and the entire night. This clause seems to differ with the rule in section two and indeed the Babylonian Talmud states that the two clauses contain two distinct opinions stemming from two different sources.