Added mcron util

tk/Makefile

@@ -1,6 +1,6 @@
 TARGET := $(shell guile -c "(display (%site-dir))")
 CCACHE := $(shell guile -c "(display(%site-ccache-dir))")
-OBJ := listlogic.go ports.go
+OBJ := listlogic.go ports.go mcron.go
 
 .PHONY: all clean install uninstall
 all: $(OBJ)

tk/mcron.scm

@@ -0,0 +1,33 @@
+(define-module (tk mcron)
+  #:export (sec/min sec/hour sec/day sec/week
+            sec/mins sec/hours sec/days sec/weeks
+            step-from
+            str->secs
+            strf->secs
+            )
+  #:use-module (srfi srfi-19)
+  #:duplicates (warn-override-core warn))
+
+(define sec/min  60)
+(define sec/hour (* 60 sec/min))
+(define sec/day  (* 24 sec/hour))
+(define sec/week (* 7 sec/day))
+
+(define (sec/mins n)  (* n sec/min))
+(define (sec/hours n) (* n sec/hour))
+(define (sec/days n)  (* n sec/day))
+(define (sec/weeks n) (* n sec/week))
+
+;; Format here refers to the format found in srfi-19 (Ref: 7.5.16.6)
+;; Literally just conversions out of (string->date)
+(define (strf->secs str format)
+  (time-second (date->time-utc (string->date str format))))
+
+(define (str->secs str)
+  (strf->secs str "~Y~m~d~H~M~S"))
+
+;; Normalize the time tm to be the next step sized increment from base.
+;; All time arguments are expected to be a time in seconds
+(define (step-from base step tm)
+  (let ((steps (truncate-quotient (- tm base) step)))
+    (+ base (* step (+ 1 steps)))))