Can you give me a GEDCOM snippet for a person with this record. I can't think why it would change by changing the range so checking the way the data is processed with something you have already tested would be the easiest to reproduce.
Edit: I suspect it is census year. Something with a year of start and end year of 1911 will be tolerated as a census year if the year option is set. Whereas something with a range of years (even if its as this case just one day more) will see if the date overlaps the census date.
The census in 1911 was 2nd April 1911 which is the date you have so I can only imagine there might be an issue with the "overlaps" check. I'll add some checks to see if I can work it out with some random test data.
Edit 2: Overlaps seems to be working with two test dates...
One other thought, a numeric month is not valid in GEDCOM could it be that your family history program is interpreting dates as American format and 02/04/1911 is export as 4 FEB 1911 instead of 2 APR 1911 that would explain not overlapping census date but I'd need to see the GEDCOM to be sure.
Edit: I suspect it is census year. Something with a year of start and end year of 1911 will be tolerated as a census year if the year option is set. Whereas something with a range of years (even if its as this case just one day more) will see if the date overlaps the census date.
The census in 1911 was 2nd April 1911 which is the date you have so I can only imagine there might be an issue with the "overlaps" check. I'll add some checks to see if I can work it out with some random test data.
Edit 2: Overlaps seems to be working with two test dates...
Code:
FactDate census = new FactDate("BET 31 Dec 1910 AND 2 APR 1911");
Assert.IsTrue(census.Overlaps(CensusDate.UKCENSUS1911));
census = new FactDate("BET 1 JAN 1911 AND 2 APR 1911");
Assert.IsTrue(census.Overlaps(CensusDate.UKCENSUS1911));
One other thought, a numeric month is not valid in GEDCOM could it be that your family history program is interpreting dates as American format and 02/04/1911 is export as 4 FEB 1911 instead of 2 APR 1911 that would explain not overlapping census date but I'd need to see the GEDCOM to be sure.