date: turn time widget argument into an offset

The os.time() call should not be passed as an argument it self,
because of a chance it will be stored internally and so we would
always get the same time. Instead we can pass time offsets in seconds,
i.e. to go 6 hours forward we can use the widget argument 21600, to go
6 hours back we use -21600 instead.

README

@@ -266,9 +266,10 @@ vicious.widgets.weather
 
 vicious.widgets.date
   - provides access to os.date, with optional time formatting provided
-    as the format string
-  - takes optional time as an argument, for example to calculate
-    time-zone differences, otherwise it formats the current time
+    as the format string - using regular date sequences
+  - takes optional time offset, in seconds, as an argument for example
+    to calculate time zone differences, otherwise current time is
+    formatted
   - returns the output of os.date(), formatted by provided sequences
 
 

widgets/date.lua

@@ -5,8 +5,11 @@
 ---------------------------------------------------
 
 -- {{{ Grab environment
-local os = { date = os.date }
 local setmetatable = setmetatable
+local os = {
+    date = os.date,
+    time = os.time
+}
 -- }}}
 
 
@@ -16,7 +19,7 @@ module("vicious.widgets.date")
 
 -- {{{ Date widget type
 local function worker(format, warg)
-    return os.date(format or nil, warg or nil)
+    return os.date(format or nil, warg and os.time()+warg or nil)
 end
 -- }}}