Added GLIBC NOTES section describing padding and width specifiers.

man3/strftime.3

@@ -228,7 +228,6 @@ E modifier is to use a locale-dependent alternative representation.
 The broken-down time structure \fItm\fP is defined in \fI<time.h>\fP.
 See also
 .BR ctime (3).
-
 .SH "RETURN VALUE"
 The \fBstrftime\fP() function returns the number of characters placed
 in the array \fIs\fP, not including the terminating NUL character,
@@ -259,6 +258,34 @@ In SUSv2, the %S specified allowed a range of 00 to 61,
 to allow for the theoretical possibility of a minute that
 included a double leap second
 (there never has been such a minute).
+.SH GLIBC NOTES
+Glibc provides a number of extensions for conversion specifiers.
+Between the % character and the conversion character, 
+an optional flag and field width may be specified.  
+(These precede the E or O modifies, if present.)
+The following flag characters are permitted:
+.TP
+.B _
+(underscore)
+Pad a numeric output string with spaces.
+.TP
+.B \- 
+(dash)
+Do not pad a numeric output string.
+.TP
+.B 0
+Pad a numeric output string with zeros even if the conversion character 
+specifies space padding.
+.TP
+.B ^
+Convert alphabetic characters in output string to upper case.
+.TP
+.B #
+Swap the case of the output string (only really useful with %Z).
+.PP
+An optional decimal width specifier may follow the (possibly absent) flag.
+If the natural size of the field is smaller than this width,
+then the output string padded (on the left) to the specified width.
 .SH BUGS
 Some buggy versions of gcc complain about the use of %c:
 .IR "warning: `%c' yields only last 2 digits of year in some locales" .