Data update

Task/Palindrome-dates/Ada/palindrome-dates.adb

@@ -0,0 +1,34 @@
+with Ada.Text_IO;
+with Ada.Calendar.Formatting;
+with Ada.Calendar.Arithmetic;
+
+procedure Palindrome_Dates is
+   Desired_Count : constant := 15;
+   Start_Date    : constant String := "2020-01-01 00:00:00";
+
+   use Ada.Calendar;
+
+   function Is_Palindrome_Date (Date : Time) return Boolean is
+      Image : String renames Formatting.Image (Date);
+   begin
+      return
+        Image (1) = Image (10) and
+        Image (2) = Image (9)  and
+        Image (3) = Image (7)  and
+        Image (4) = Image (6);
+   end Is_Palindrome_Date;
+
+   Date  : Ada.Calendar.Time := Formatting.Value (Start_Date);
+   Count : Natural := 0;
+
+   use type Ada.Calendar.Arithmetic.Day_Count;
+begin
+   loop
+      if Is_Palindrome_Date (Date) then
+         Ada.Text_IO.Put_Line (Formatting.Image (Date) (1 .. 10));
+         Count := Count + 1;
+      end if;
+      exit when Count = Desired_Count;
+      Date := Date + 1;
+   end loop;
+end Palindrome_Dates;

Task/Palindrome-dates/Crystal/palindrome-dates.cr

@@ -0,0 +1,10 @@
+count = 0
+(2020..).each do |year|
+  digits = year.digits
+  month = digits[0]*10 + digits[1]
+  next unless 1 <= month <= 12
+  day = digits[2]*10 + digits[3]
+  next unless 1 <= day <= Time.days_in_month(year, month)
+  puts "%4d-%02d-%02d" % {year, month, day}
+  break if (count += 1) == 15
+end

Task/Palindrome-dates/Fortran/palindrome-dates.f

@@ -0,0 +1,109 @@
+!
+! Palindrome dates
+! tested with Intel ifx (IFX) 2025.2.1 20250806             on Kubuntu 26.04
+!             GNU gfortran (Ubuntu 15.2.0-16ubuntu1) 15.2.0 on Kubuntu 26.04
+!             VSI Fortran x86-64 V8.7-001                   on OpenVMS V9.2-3
+! U.B., April 2026
+!
+program PalindromeDates
+implicit none
+
+integer :: yyyy, mm, dd
+integer :: nPals=0
+
+yyyy=2030                                           ! Start value, for 1st palindromic date after 2020-02-02
+
+do while (nPals .lt. 15 .and. yyyy .lt. 10000)      ! year 10000 would produce run-time error
+  call yyyytommdd (yyyy,mm,dd)                      ! calculate mm,dd from yyyy so that yyyymmdd is a palindrome
+  if (isPlausibleDate (yyyy,mm,dd)) then            ! exclude invalid dates such as 2031-13-02 or 4321-12-34
+    write (*, '(I4,"-",i2.2,"-",i2.2)') yyyy,mm,dd  ! print the rest: valid palindromic dates
+    nPals = nPals + 1                               ! Count valid palindromic dates
+  end if
+  yyyy = yyyy+1                                     ! Try again next year
+enddo
+
+contains
+
+
+! =========================================
+! Decide if a given date Y-m-d is plausible
+! =========================================
+function isPlausibleDate (y,m,d) result (YN)
+integer, intent(in) :: y,m,d
+logical :: YN
+
+! Max number of Days in each month, Feb is 29 in leap years only.
+integer, dimension(12),parameter :: nDays =[31,29,31,30,31,30,31,31,30,31,30,31]
+
+YN = .false.
+
+if (m .lt. 1 .or. m .gt. 12) then           ! Impossible Month
+  return                                    ! Early return .false.
+endif
+
+if (d .lt. 1 .or. d .gt. nDays(m)) then     ! Impossible day
+  return                                    ! Early return .false.
+endif
+
+! Special case: feb-29
+if (m .eq. 2 .and. d .eq. 29) then        ! 20-Feb: only OK if Y is a leap year
+  ! Check for leap year
+  if (isLeapYear (y)) then
+    YN = .true.                           ! in a leap year, Feb 29 is correct date
+  else
+    return                                ! Early return .false.
+  endif
+endif
+!
+! Any date not excluded by now is plausible.
+!
+YN = .true.
+
+end function isPlausibleDate
+
+
+! ===============================
+! Decide if year y is a leap year
+! ===============================
+function isLeapYear (y) result (YN)
+integer, intent(in) :: y
+logical :: YN
+!
+! Rule: A year is a leap year if it is divisible by 4,
+!       unless it is divisible by 100 but not by 400.
+! e.g. 1900 is NOT a leap year
+YN = (mod (y, 4) .eq. 0 .and. (mod(y, 400) .eq. 0 .or. mod(y, 100) .ne. 0))
+
+end function isLeapYear
+
+! =====================================================================
+! calculate month m,day d from year y so that yyyymmdd is a palindrome
+! =====================================================================
+subroutine yyyytommdd (y,m,d)
+integer, intent(in) :: y
+integer, intent(out) :: m,d
+
+character(len=4) strYear, raeYrts
+
+
+write (strYear, '(i4)')   y       ! Convert integer Year to string
+raeYrts = reverse (strYear)       ! reverse order of characters in strYear so that strYearraeYrts is palindrome
+read (raeYrts, '(i2,i2)')   m, d  ! extract integer month m and day d from reversed year
+
+end subroutine yyyytommdd
+
+! ==========================================================================
+! return a 4-letter string in the reverse order of its letters: abcd -> dcba
+! ==========================================================================
+function reverse (chr) result(rhc)
+character (len=4), intent(in) :: chr
+character (len=4) :: rhc
+integer :: ii
+
+do ii=1, 4
+  rhc(ii:ii) = chr (5-ii:5-ii)
+enddo
+
+end function reverse
+
+end program PalindromeDates

Task/Palindrome-dates/Frink/palindrome-dates.frink

@@ -0,0 +1,13 @@
+d = #2020-02-02 12:00#
+count = 0
+
+do
+{
+   d = d + 1 day
+   str = (d -> ### yyyyMMdd ###)
+   if str == reverse[str]
+   {
+      println[d -> ### yyyy-MM-dd ###]
+      count = count + 1
+   }
+} until count == 15

Task/Palindrome-dates/Rust/palindrome-dates.rs

@@ -1,18 +1,18 @@
 // [dependencies]
-// chrono = "0.4"
+// chrono = "0.4.44"
 
 fn is_palindrome(s: &str) -> bool {
     s.chars().rev().eq(s.chars())
 }
 
 fn main() {
-    let mut date = chrono::Utc::today();
+    let mut date = chrono::Utc::now().date_naive();
     let mut count = 0;
     while count < 15 {
         if is_palindrome(&date.format("%Y%m%d").to_string()) {
             println!("{}", date.format("%F"));
             count += 1;
         }
-        date = date.succ();
+        date = date.succ_opt().unwrap();
     }
 }

Task/Palindrome-dates/V-(Vlang)/palindrome-dates.v

@@ -0,0 +1,21 @@
+import time
+
+fn is_palindrome(sg string) bool {
+    return sg == sg.reverse()
+}
+
+fn main() {
+	limit := 15
+    mut dt, mut num := 0, 0
+    println("First 15 palindromic dates:\n")
+    for num < limit {
+        dt++
+        date := time.now().add_days(dt)
+        new_date := "${date.year:04}${date.month:02}${date.day:02}"
+        new_date_2 := "${date.year:04}-${date.month:02}-${date.day:02}"
+        if is_palindrome(new_date) {
+            num++
+            println(new_date_2)
+        }
+    }
+}