I guess the key thing to bear in mind is: https://docs.oracle.com/en/java/javase/20/docs/api/java.base/java/util/Calendar.html """ The calendar field values can be set by calling the set methods. Any field values set in a Calendar will not be interpreted until it needs to calculate its time value (milliseconds from the Epoch) or values of the calendar fields. Calling the get, getTimeInMillis, getTime, add and roll involves such calculation. """
Calendar doesn't provide a way to differentiate, in other words. See default values for fields at https://docs.oracle.com/en/java/javase/20/docs/api/java.base/java/util/GregorianCalendar.html Calendar is often used as a ' bucket' for timey-wimey things: you stuff things into fields that contextually make sense and ignore those that don't. Not very nice OO or helpful as an API. It MAY be (speaking off the top of my head here) that you don't need/want Calendar...the newer java.time package has many "finer-grained" classes for things like Instance, Period, Duration, etc. that might be a better fit for a specific use-case: https://www.baeldung.com/java-8-date-time-intro BOB ________________________________ From: James McMahon <jsmcmah...@gmail.com> Sent: Tuesday, 20 June 2023 8:53 AM To: users@groovy.apache.org <users@groovy.apache.org> Subject: Working with Calendar object in Groovy If I have a Calendar object created for 1999-01-01, a get() of calendar.MONTH will return 0. From references I’ve found through Google, we have to add 1 to MONTH to get the 1 for January. The calendar object has 0 for MONTH. Now let’s take the case where we set our calendar object from “1999”,. When we get MONTH it is also 0 - but not because our month was January, but because it was not present. How does the calendar instance differentiate between those two cases? Is there another calendar object element that tells me “hey, I could set no day or month from a date like 1999”?
