JavaPeriodGetDays

A java.time.Period represents a distance of civil time in years, months, and days. For example, a period could represent "1 month, 2 days", or another period could represent "32 days".

The method Period.getDays() only extracts the "days" portion of the Period, so a period representing "1 month, 2 days" would return 2 from its getDays().

In many circumstances, developers use period.getDays() when they think it represents "the total days" in the period, especially when the Period is computed using LocalDate.until(LocalDate).

In this instance, a developer has used period.getDays() without consulting either the months or years portion of the Period. In all likelihood, the developer would be better suited by using org.threeten.extra.Days.between(LocalDate, LocalDate) to compute the number of days between two dates.

For example:

LocalDate day1, day2; ...
if (day1.until(day2).getDays() > 31) { // No more than 31 days between them
  // Oops, this is always false, even if day1 is 4 "months" behind
}

if (Days.between(day1, day2).compareTo(Days.of(31)) > 0) {
  // Can actually be executed!
}