Time and Date Expressions – today / now

today / now

In Rainbird, concepts can be ‘date’ concepts.  Date concepts should be used when a date will be either input into or output by Rainbird.  Rainbird can use date expressions to transform and calculate dates. Date expressions can be combined with other date, transformative and comparative expressions to ‘retrieve’, ‘add’,  ‘subtract’ or ‘compare’ time. This article will focus on two date expressions, today() and now():

  • today(): Rainbird is able to generate today’s date at midnight as a value (e.g. if it’s the 2nd of February 2021, Rainbird would generate 2021-02-02 00:00:00) and use the value in expressions.
  • now(): Rainbird is able to generate the date and time the query is run at as a value(e.g. if it’s the 2nd of February 2021 12PM, Rainbird would generate 2021-02-02 12:00:00) and use the value in expressions.
When using today() or now() in expressions that use number and/or string concepts, Rainbird will convert the date/time to the amount of milliseconds from the 1st of January 1970 to either 00:00:00 on today’s date for today() or the date and time the query is run on for now() (e.g. if we were using the today() expression in a rule and ran the query on the 1st of March 2021, Rainbird would count 1614556800000 milliseconds from 1970-01-01 to 2021-03-01 00:00:00). The output of a query using dates will vary dependent on output concept type.

To convert a milliseconds result to a more useful integer of time divide the value by:
  • 1000 (seconds) 
  • 60000 (minutes) 
  • 3600000 (hours) 
  • 86400000 (days)
  • 31536000000 (years).
E.g. To convert a now() result from milliseconds to years, the sum would be ‘now() / 31536000000’; the result of the sum would be the number of years between the time the query is run and the 1st of January 1970 (see the working with milliseconds section for more information).

To demonstrate the today() and now() expressions, let’s build a map that will return a different greeting, depending on what time of the day the query is run at.

First, create two string concepts: ‘Person’ and ‘Greeting’. Next, connect the concepts with a relationship, ‘says’:

Figure 1: ‘Person’ and ‘Greeting’ concept linked with ‘says’ relationship  

Next, create three concept instances for the concept ‘Greeting’:

Figure 2: ‘Greeting’ concept instances

The three rules that the map will use are built on the relationship ‘says’.

Rainbird will work out what time of day it is, by comparing the value generated by the today() expression with the value generated by the now() expression.

Each rule needs a now() expression, as Rainbird will need to first work out what time it currently is. The expression is assigned to the variable %NOW:

Figure 3: now() expression for ‘good morning’ rule

Each rule will also need a today() expression, as Rainbird will compare the now() value with the today() value, to see how many hours have passed in the day. As the value generated by the today() expression will be the time at midnight, the value will be assigned to the variable %MIDNIGHT:


Figure 4: today() expression for ‘good morning’ rule

Now that we have created the expressions which will generate the values and assign the values to the variables %MIDNIGHT and %NOW, we need to use another expression to compare the two values. The Date Expressions ‘hoursBetween’ will count every full hour between the first hour of today’s date (%MIDNIGHT) and the time that the query is run (%NOW). The value calculated by the expression is assigned to the value %HOURS:

Figure 5: hoursbetween expression comparing the hours between %NOW and %MIDNIGHT

The %HOURS value will be the value compared with the hours of the day. We only want the map to return a ‘good morning’ result if the query is run before 12PM. So, the %HOURS value needs to be less than 12. Therefore, the final part of the rule would be:

 Good morning:

Figure 6: %HOURS less than 12 expression

To create the two rules for the ‘good afternoon’ and ‘good evening’ concept instances, follow the same steps above but change the final comparative expression, depending on the object of the rule.

Good afternoon:

Figure 7: Good afternoon comparative expression

Good evening:

Figure 8: Good evening comparative expression

The ‘says’ query will return a different result, depending on when the query is run:

Figure 9: Result after running the main query ‘says’ before 12pm

Rainbird will output the values generated by the today() and now() expressions as the number of milliseconds passed since 1st of January 1970 to today’s date at midnight for today() or the current date and time for now().

If you create a relationship between the person concept and the greeting concept used in the example map, and add the today() value as the sole expression in the relationship’s rule, and assign the value to %O, when running the query, Rainbird will return the millisecond value:

Figure 8: Millisecond value

The value can be converted into a more useful integer. To convert the value, create another relationship, ‘transformed in years’.  To the rule on the ‘transformed in years’ relationship, add the following expressions:

Figure 9: Expressions to transform millisecond value to years and return the result as a string concatenation

You will need to assign the variable of the today() expression to %YEARS as Rainbird will use the %YEARS value in a string concatenation (the second expression), which will be the output of the query. The string concatenation will be assigned to the %O variable (the object of the relationship), as this is what we want Rainbird to return as a result.

Now, if you run the ‘transformed in years’ query, Rainbird will provide the following answer:

Figure 10: Transformed result

The RBLang below will generate the map that was built in the article. Click on ‘

Click on the ‘Export.rbird’ button to download the ‘today/now’ map used in this example. The knowledge map can then be imported into your Rainbird Studio.

Export .rbird’ to download the knowledge map, or ‘copy RBLang’ and paste the code directly into Rainbird.

Query and Results

The query that will return a greeting depending on the time of day is on the ‘says’ relationship. The other two relationships, today and now, will display the date/current time in milliseconds.

Article Feedback form
Did you find this article useful?

Version 1.04 – Last Update: 29/03/2021