Data update

Task/Five-weekends/DuckDB/five-weekends.duckdb

@@ -0,0 +1,19 @@
+create or replace function day_before(day) as (6+day) % 7;
+
+create or replace function weekday_of_last_day_of_month(year, month) as (
+  if(month=12,
+     day_before( extract('dayofweek' from make_date(year+1, 1, 1) )),
+     day_before( extract('dayofweek' from make_date( year, month+1, 1 ) ) ))
+);
+
+# The only case where the month has 5 full weekends is when the last day
+# of the month falls on a Sunday (0) and the month has 31 days.
+#
+create or replace function five_weekends(start, stop) as table (
+  select year, month
+  from range(start, stop) as t(year),
+       unnest([1,3,5,7,8,10,12]) as u(month) -- months with 31 days
+  where weekday_of_last_day_of_month(year, month) = 0
+);
+
+from five_weekends(1900, 2101) order by year, month;

Task/Five-weekends/FutureBasic/five-weekends.basic

@@ -0,0 +1,54 @@
+//
+// Calculate months having 5 Fridays,
+//                   5 Saturdays, and 5 Sundays
+//                   from year 1900 through 2100
+//
+//=================================================================
+// DayOfTheWeek - returns day of the week (Gregorian only)
+//
+// on entry: month, day, year
+// on  exit: result = index to days
+//                     (0 = Sat, 1 = Sun,... 5 = Thu, 6 = Fri)
+//
+local fn DayOfTheWeek (month as Int, day as Int, year as Int) as int
+  Int result
+  if month < 3 then month+=12: year--
+  result = (day +  fix(((month + 1) * 13) / 5) + year ¬
+  + fix(year / 4) - fix(year / 100) + fix(year / 400)) % 7
+end fn = result
+
+CFStringRef MonthNames(12) = {@"Greg Months",@"January",@"February",¬
+@"March",@"April",@"May",@"June",@"July",¬
+@"August",@"September",@"October",¬
+@"November", @"December"}
+
+window 1,@"Five weekends"
+print
+
+Int x, mm, yyyy
+Int tot, none
+CFStringRef res
+
+for yyyy = 1900 to 2100
+  res = @""
+  for mm = 1 to 12 step 2
+    if mm == 9 then mm = 8
+    if fn DayOfTheWeek(mm,1,yyyy) == 6
+      res = concat (res,MonthNames(mm), @" ")
+      tot++
+    end if
+  next mm
+  if len(res) < 1 then none++
+  if ((yyyy < 1906) && (len(res) > 1)) || ((yyyy > 2094) && (len(res) > 1))
+    print "Year ";yyyy;": ";: print res
+  else
+    if yyyy % 30 == 0 then print " ..."
+  end if
+next yyyy
+
+print
+print "=========================="
+print "Total months with   = " ;tot
+print "Total years without =  ";none
+
+handleEvents

Task/Five-weekends/Red/five-weekends.red

@@ -0,0 +1,36 @@
+Red [ "Five Weekends - Hinjo, 20 July 2025" ]
+
+; get day from year, month, week, and weekday!
+getday: function [y[integer!] m[integer!] w[integer!] wd[integer!]] [
+	fd: to-date reduce [1 m y] ; first day!
+	swd: fd/weekday + 1  if swd > 7 [swd: 1] ; shift from mon=1 to sun=1
+	ofs: (w - 1) * 7 + (wd - swd) ; offset
+	d: fd + ofs ; date
+	either d/month = m [d/day] [0] ; return day or zero!
+]
+
+mo: system/locale/months
+tfw: 0 ; total five weekends
+boring: 0 ; total boring years
+awesome: 0 ; total owesome years
+
+y: 1900  while [y <= 2100] [  fwy: 0 ; five weekends in year
+	prin [y]
+    foreach m [1 3 5 7 8 10 12] [
+		if 1 = d: getday y m 1 6 [  fwy: fwy + 1
+			prin [" " mo/:m]
+        ]
+    ]
+	tfw: tfw + fwy
+	either fwy > 0 [
+		print [" ==> Five weekends: " fwy]
+		if fwy > 1 [ awesome: awesome + 1]
+	][
+		boring: boring + 1
+		print [" ==> Boring year!"]
+	]
+	y: y + 1
+]
+print ["Total five weekends: " tfw]
+print ["Total boring years: " boring]
+print ["Total years with multiple five weekends months: " awesome]