There are a few DateTime related data types in M: DateTime, Date and Time. Each datatype has it’s own functions to extract parts like Year, Month and Quarter or calculate with Date/Times. For a full list of Date/Time functions: DateTime functions, Date functions. 

let
    // DateTime:
    varNow = DateTime.LocalNow(),                                 // 2023-03-06T08:39:21.9808139

    // Date: 
    varToday = Date.From(varNow),                                 // 06-03-2023
    varYear = Date.Year(varNow),                                  // 2023
    varMonth = Date.Month(varNow),                                // 3
    varMonthname = Date.ToText(varToday,"MMMM"),                  // March
    varYesterday = Date.AddDays(varToday, -1),                    // 05-03-2023
    varYesterday = Date.AddMonths(varToday, 1),                   // 06-04-2023    
    varStartOfYear = Date.StartOfYear(varToday),                  // 01-01-2023
    varEndOfYear = Date.EndOfYear(varToday),                      // 31-12-2023    
    varBirthDate =  #date(1974,9,2),                              // 02-09-1974

    // Time: 		
    varTime = Time.From(varNow),                                  // 08:39:21.9808139
    varEndOfWorkTime = #time(17,0,0 ),                            // 17:00:00

If you substract 2 Date or Time objects you get a Duration object. From this Duration object you can get the total days, hours, minutes and seconds. For a full list of Duration Functions: Duration functions – PowerQuery M | Microsoft Learn

    // Duration:
    varDuration = Duration.TotalDays(varToday - varBirthDate) ,     // 17717
    varHoursLeft = Duration.TotalHours( varEndOfWorkTime - varTime) // 8.3443580742777783
  in
    varHoursLeft