diff --git a/share/completions/date.fish b/share/completions/date.fish
index d033932d8..ed1a0f043 100644
--- a/share/completions/date.fish
+++ b/share/completions/date.fish
@@ -1,22 +1,41 @@
+complete -c date -f -d "display or set date and time"
 if date --version > /dev/null 2>/dev/null
 	complete -c date -s d -l date -d "Display date described by string" -x
 	complete -c date -s f -l file -d "Display date for each line in file" -r
-	complete -c date -s I -l iso-8601 -d "Output in ISO 8601 format" -x -a "date hours minutes seconds"
+	complete -c date -s I -l iso-8601 -d "Output in ISO-8601 format" -x -a "date hours minutes seconds"
 	complete -c date -s s -l set -d "Set time" -x
-	complete -c date -s R -l rfc-2822 -d "Output RFC-2822 compliant date string"
-	complete -c date -s r -l reference -d "Display the last modification time of file" -r
-	complete -c date -s u -l utc -d "Print or set Coordinated Universal Time"
-	complete -c date -l universal -d "Print or set Coordinated Universal Time"
-	complete -c date -s h -l help -d "Display help and exit"
-	complete -c date -s v -l version -d "Display version and exit"
-else # OS X
-	complete -c date -s d -d 'Set the kernel\'s value for daylight saving time' -x
-	complete -c date -s f -d 'Use format string to parse the date provided rather than default format'
-	complete -c date -s j -d 'Do no try to set the date'
-	complete -c date -s n -d 'Set the time for current machine only in the local group'
-	complete -c date -s r -d 'Print date and time represented by SEC since Epoch' -x
-	complete -c date -s t -d 'Set system\'s value for MINUTES west of GMT'
-	complete -c date -s u -d 'Display or set the date int UTC time'
-	complete -c date -s v -d 'Adjust the time component backward(-)/forward(+) according to VAL' -x
+	complete -c date -s R -l rfc-2822 -d "Output RFC-2822 date string"
+	complete -c date -s r -l reference -d "Display last modification time of file" -r
+	complete -c date -s u -l utc -d "Print/set UTC time" -f
+	complete -c date -l universal -d "Print/set UTC time" -f
+	complete -c date -s h -l help -d "Display help and exit" -f
+	complete -c date -s v -l version -d "Display version and exit" -f
+else
+	complete -c date -s u -d 'Display or set UTC time' -f
+	complete -c date -s j -d "Don't actually set the clock" -f
+	complete -c date -s d -d "Set system's value for DST" -x
+
+	set -l uname (uname -s)
+
+	test "$uname" != OpenBSD
+	and complete -c date -s n -d 'Set clock for local machine only' -f
+
+	switch $uname
+		case FreeBSD Darwin DragonFly
+			# only -u is actually POSIX. Rest are BSD extensions:
+			complete -c date -s r -d "Show file mtime, or format seconds" -r
+			complete -c date -s v -d 'Adjust clock +/- by time specified' -f
+		case NetBSD OpenBSD
+			complete -c date -s a -d "Change clock slowly with adjtime" -x
+			complete -c date -s r -d "Show date given seconds since epoch" -x
+			if test "$uname" = NetBSD
+				complete -c date -s d -d "Parse human-described date-time and show result" -x
+				exit
+			end
+			complete -c date -s z -d "Specify timezone for output" -x
+	end
+	
+	complete -c date -s t -d "Set system's minutes west of GMT" -x
+	complete -c date -s f -d 'Use format string to parse date' -f
 end