use UTC for now

i don't like this, but it's my best option to make things mostly monotonic.

README.md

@@ -342,11 +342,11 @@ will take a date or a file as an argument too.
 
 ```
 $ now
-2016-06-27_19551873
-$ now ./now
-2016-03-12_25288645
+2019-05-27_35083906
+$ now ~/sh/monitor
+2017-03-14_82387259
 $ now '@1234567890'
-2009-02-13_55890000
+2009-02-13_84690000
 ```
 
 ### [pacbm](/sh/pacbm)

sh/now

@@ -4,11 +4,11 @@ now() {
     local dt=
     local fmt='+%F_%T_%N'
     if [ -z "$1" ]; then
-        dt="$(date "$fmt")"
+        dt="$(date -u "$fmt")"
     elif [ -e "$1" ]; then
-        dt="$(date -r "$1" "$fmt")"
+        dt="$(date -u -r "$1" "$fmt")"
     else
-        dt="$(date -d "$1" "$fmt")"
+        dt="$(date -u -d "$1" "$fmt")"
     fi
 
     local F= T= N=