On 6/11/19 1:14 PM, Guy Harris wrote:
Are there any countries that do both seasonal adjustment *and* Ramadan adjustment *in the same year*?
Morocco did that from 2013 through October 2018. That is, they sprang forward on March's last Sunday and fell back on October's last Sunday; and they also fell back before Ramadan and sprang forward afterward, so that there were four transitions per year. Egypt did something similar in 2010 and in 2014, as did Palestine's West Bank in 2011. tzdb can specify this succinctly, as any number of rules can apply during a year. CLDR+Java can handle this situation too (I don't know how, but I just now checked Morocco in 2017 and it worked OK). POSIX TZ strings cannot handle it, though, as POSIX provides for only two transitions per year. It's a bit of a mess to do it, partly because the Islamic calendar is astronomical and not algorithmic, and quite possibly we won't see anything similar in the near future with DST transitions falling out of favor in Europe anyway.