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https://issues.apache.org/jira/browse/CALCITE-1884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16342050#comment-16342050
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Julian Hyde commented on CALCITE-1884:
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I added the following to {{DateTimeUtilsTest.testDateToString}}.
{noformat} final int d1900 = -(70 * 365 + 70 / 4);
final int century = 100 * 365 + 100 / 4;
checkDateString("1900-01-01", d1900);
// +1 because 1800 is not a leap year
final int d1800 = d1900 - century + 1;
checkDateString("1800-01-01", d1800);
final int d1700 = d1800 - century + 1;
checkDateString("1700-01-01", d1700);
final int d1600 = d1700 - century;
checkDateString("1600-01-01", d1600);
final int d1500 = d1600 - century + 1;
checkDateString("1500-01-01", d1500); // fails, about 10 days off
{noformat}
It all succeeds except 1500-01-01, which is about 10 days off. It looks as if
your code has a gap at the gregorian cutover, 1582-10-15. PostgreSQL does not
have this gap, because it stays in "new style":
{noformat}
select date '1900-01-01' - 109573 * interval '1' day as d # returns 1600-01-01
select date '1900-01-01' - 115859 * interval '1' day as d # returns 1500-10-16
select date '1900-01-01' - 115860 * interval '1' day as d # returns 1500-10-15
select date '1900-01-01' - 115861 * interval '1' day as d # returns 1500-10-14
select date '1900-01-01' - 146097 * interval '1' day as d # returns 1500-01-01
{noformat}
> DateTimeUtils produces incorrect results for days before Gregorian cutovers
> ---------------------------------------------------------------------------
>
> Key: CALCITE-1884
> URL: https://issues.apache.org/jira/browse/CALCITE-1884
> Project: Calcite
> Issue Type: Bug
> Components: avatica
> Affects Versions: 1.13.0
> Reporter: Haohui Mai
> Assignee: Haohui Mai
> Priority: Major
>
> dateStringToUnixDate() / unixDateToString() do not return consistent result.
> The following test fails:
> {noformat}
> @Test public void testUnixDate() {
> int days = DateTimeUtils.dateStringToUnixDate("1500-04-30");
> assertEquals("1500-04-30", DateTimeUtils.unixDateToString(days));
> }
> {noformat}
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