Document the time module.

doc/utils.md

@@ -73,3 +73,20 @@ remainder with leading whitespace removed.
 ### Tag
 
 ### Time
+
+    (import util-time)
+
+Compatibility module for the differences between chicken scheme
+version 5.2 and earlier and 5.3 and on.
+
+    (current-util-milliseconds)
+
+Returns the number of milliseconds since process startup.
+
+Under chicken scheme <5.3 it uses ```current-milliseconds``` and for
+chicken scheme >=5.3 it uses ```current-process-milliseconds```.
+
+Without this module compilation with ```current-milliseconds```
+results in warnings on chicken scheme >=5.3 and compilation under
+chicken scheme <5.3 results in error with
+```current-process-milliseconds```.