Julia Date and Time

Julia provides the following three functions to handle dates and times through the Dates module:

• Date: Indicates a date, accurate to the day, and only displays the date.
• DateTime: Indicates date and time, accurate to milliseconds.
• DateTime: Indicates the time of day, accurate to nanoseconds, representing a specific moment in the 24 hours of a day.

Before using it, we need to import the Dates module first:

import Dates

Date and DateTime types can be parsed from integers or Period types.

Period is based on date values and represents years, months, days, etc.:

Period
Year
Quarter
Month
Week
Day
Hour
Minute
Second
Millisecond
Microsecond
Nanosecond

Both Date and DateTime are subtypes of the abstract type TimeType.

The following diagram shows the relationship between date types; click the image to enlarge it:

The following table gives date format codes, through which we can format our dates:

Through the above examples, we created some date/time objects. Next, we can use these objects to obtain data (including year, month, day, minute, second, hour, etc.):

Date Arithmetic

We can perform arithmetic operations on date objects.

For example, we calculate the number of days between two dates:

We can also add to dates, for example, calculate the date after 2 years and 6 months:

Date Ranges

Julia can create dates for a specified interval using iterable range objects. In the example given below, we will create an iterator that generates the first day of each month.

In the range object above, we can find which ones are weekdays. Here we need to create an anonymous function for filter() that determines whether it is a weekday based on the given date:

Rounding Dates and Times

We often use round(), floor(), and ceil() functions to round parameters up or down. Similarly, these functions can also be used to round dates, so as to adjust dates forward or backward in time.

ceil()The function will adjust the date/time forward, as shown below:

Repeating Dates

We can find repeating dates within a range, for example, every Sunday:

UNIX time, or POSIX time, is a time representation used by UNIX or UNIX-like systems: the total number of seconds from 0:00:00 on January 1, 1970 UTC to the present, ignoring leap seconds.

The time() function returns the Unix value:

The unix2datetime() function converts Unix time to a date/time object:

Current Time

DateTimes are measured in milliseconds; we can use the Dates.value function to get the time in milliseconds:

Time and Monitoring

Julia provides us with@elapsedmacro, which returns the time (in seconds) required to execute an expression.

Calculate the time required to execute the following code:

More Examples