entryHeader time setter more tolerant

* Allows parameter to the `time` setter to be any parameter accepted by the `Date` constructor
* Re-instates the functionality removed at:
6e717ad#diff-6af03ff88c79ec964bc6482f32561df5347e564bd58f5aa1e1801682d4c49842L33
* Closes #539

Author: thomasheritage

headers/entryHeader.js

@@ -98,6 +98,7 @@ module.exports = function () {
             return Utils.fromDOS2Date(this.timeval);
         },
         set time(val) {
+            val = new Date(val);
             this.timeval = Utils.fromDate2DOS(val);
         },