remove Mountain Daylight Time

ch04.adoc

@@ -192,7 +192,7 @@ It must comprise a unit of measure that is physically equivalent to the SI base
 There is no default value for the **`units`**.
 These requirements can best be described by an example with explanatory comments:
 
-The time unit specification **`seconds since 1992-10-8 15:15:42.5 -6:00`** indicates seconds since October 8th, 1992  at  3 hours,  15 minutes  and  42.5 seconds in the afternoon in the time zone which is six hours to the west of Coordinated Universal Time (i.e.  Mountain Daylight Time).
+The time unit specification **`seconds since 1992-10-8 15:15:42.5 -6:00`** indicates seconds since October 8th, 1992  at  3 hours,  15 minutes  and  42.5 seconds in the afternoon in the time zone which is six hours to the west of UTC.
 The time zone specification can also be written without a colon using one or two digits (indicating hours) or three or four digits (indicating hours and minutes).
 
 The acceptable units for time are given by the UDUNITS package.