Daily cron expression with timezone offset displays incorrect day

[khOst]

Cron Expression 0 20 28 * * with a tzOffset set to 5

Expected Output "At 01:00 AM, on day 29 of the month"

Actual Output "At 01:00 AM, on day 28 of the month"

Prerequisites

• [x] The cron expression being passed in is a valid expression. cRonstrue does not validate expressions and assumes the one you pass is already valid. See the FAQ for more details.

[bradymholt]

Isn't this correct? With tzOffset set to 5 and hour set to 20, this would cause the time to move to the next day. This was implemented / changed in https://github.com/bradymholt/cRonstrue/pull/296.

[khOst]

Sorry, expected and actual should be switched in places, I've updated the description. The time is expected to move to next day, but cRonstrue returns the same day, despite the offset.

[khOst]

Also for a negative tzOffset instead of returning the same day, it should return the previous day. For example, day 27 is expected here https://runkit.com/65a61ad4cca25b00082679bc/65a61ae3fdc4a20008bebfa5.

[bradymholt]

@maxtwardowski - Do you think changes in https://github.com/bradymholt/cRonstrue/pull/296 need to be tweaked for this case?

[ZaneGeiser]

Hi @bradymholt, I just started using this package (tyvm for building it!) this week and noticed this same issue.

I wrote some test that I think would need to pass in order for this issue to be resolved.

    it("5 23 1 * *", function() {
      assert.equal(cronstrue.toString(this.test?.title as string, {
        tzOffset: 2,
      }), "At 01:05 AM, on day 2 of the month")
    });

    it("5 23 31 * *", function() {
      assert.equal(cronstrue.toString(this.test?.title as string, {
        tzOffset: 2,
      }), "At 01:05 AM, on day 1 of the month")
    });

    it("5 23 1 * *", function() {
      assert.equal(cronstrue.toString(this.test?.title as string, {
        tzOffset: -2,
      }), "At 11:05 PM, on day 31 of the month")
    });

I went to try making the code change but noticed there are some special day-of-month cases (like L, WL, and LW), and wasn't sure how it would need to fit in with those cases.

[ZaneGeiser]

As I think about it more, it probably needs to wrap the L day of the month forward to 1 if the tzOffset pushes over the dateline.

Ie, if L is converted to the day before the last day, then it should remain as the Last day. But if L is converted to the day after the last day then it should write 'day 1 of the month'.

Or as tests:

    it("5 23 L * *", function() {
      assert.equal(cronstrue.toString(this.test?.title as string, {
        tzOffset: -2,
      }), "At 01:05 AM, on the last day of the month")
    });

    it("5 23 L * *", function() {
      assert.equal(cronstrue.toString(this.test?.title as string, {
        tzOffset: 2,
      }), "At 01:05 AM, on day 1 of the month")
    });

[kbazzani]

First, very useful package, keep up the good work!

Second, here are a couple more examples. Along with the day of the month as previously mentioned, the month also doesn't wrap correctly.

construe.toString( "59 23 31 12 3", { locale:"en", tzOffset: 1} ) 'At 12:59 AM, on day 31 of the month, and on Thursday, only in December'

Should be Jan 1st

construe.toString( "01 00 01 01 3", { locale:"en", tzOffset: -1} ) 'At 11:01 PM, on day 01 of the month, and on Tuesday, only in January'

Should be Dec 31st.

Best!