# How to calculate time difference by using a formula

Date and time formulas are useful for managing features that are time or date dependent. Two data types are used for working with dates and time in MobiDB: these are Date and Time types. You can use operations like addition or subtraction on Date and Time values to calculate either a future date or elapsed time between two dates.

The date value acquired from the Date type field holds only date as such, but during the calculation, if you add a Time type value to a Date type value it is possible to get a combined Date/Time value.

The following properties are available when working with Date type:

day – returns the day of the month of a given date (21.01.2015 12:01 -> 21)
month – returns the month of given date (21.01.2015 12:01 -> 1)
year – returns the year of a given date (21.01.2015 12:01 -> 2015)
date – returns the date, that does not have a time shift (21.01.2015 12:01 -> 21.01.2015)
time – returns the time shift from 0:00 date (21.01.2015 12:01 -> 12:01)

The values of Date type do not have any methods.

The available operations include:

addition to time – results in a date, shifted forward for a given time
subtraction of time from date – results in a date, shifted backward for a given time
subtraction of date from date – results in a time, elapsed from the subtracted date

The following comparison operators are supported: <, >, <=, >=

Time type in general is represented by a time interval. When getting the time value from the Time type field the value can fall within 00:00:00 to 23:59:59, but during the expression calculation the result may be more than one day.

The following properties are available when working with Time type:

days – returns a number of days in a given time interval (1d 12:02:15 -> 1)
hours – returns a number of hours in a given time interval (1d 12:02:15 -> 12)
minutes – returns a number of minutes in a given time interval (1d 12:02:15 -> 2)
seconds – returns a number of seconds in a given time interval (1d 12:02:15 -> 15)
totalhours – returns  a total number of hours of a given time interval (1d 12:01:15 -> 36)
totalminutes – returns  a total number of minutes of a given time interval (1d 12:01:15 -> 2161)
totalseconds – returns  a total number of seconds of a given time interval (1d 12:01:15 -> 129675)

The values of the Time type do not have any methods.

The available operations for Time type include:

unary -, addition to another time interval, subtraction from time interval.

Let’s have a look at the sample for better perception.

Task. To calculate worktime hours by subtracting date and time values.

In this scenario we originally have the following fields in our database:

Start date (‘date1’ field) of Date type
Start time (‘time1’ field) of Time type
End date (‘date2’ field) of Date type
End time (‘time2’ field) of Time type

To calculate working hours (subtract Start date and time from End date and time) the following approach can be used:

1.Use days property to get the number of days and multiply the result by 24 to get the number of hours
2.Subtract Start time from End time and use hours property to get the number of hours
3.Add the results  from step 1 and 2 to get the total working hours value

(date2-date1).days*24+(time2-time1).hours