diff --git a/man5/tzfile.5 b/man5/tzfile.5
index 46e083930..7c129e200 100644
--- a/man5/tzfile.5
+++ b/man5/tzfile.5
@@ -3,8 +3,6 @@
 .\" 1996-06-05 by Arthur David Olson <arthur_david_olson@nih.gov>.
 .\" %%%LICENSE_END
 .\"
-.\" @(#)tzfile.5	7.11
-.\"
 .TH TZFILE 5 2017-08-04 "" "Linux Programmer's Manual"
 .SH NAME
 tzfile \- timezone information
@@ -59,12 +57,12 @@ The number of local time types for which data entries are stored
 in the file (must not be zero).
 .TP
 .I tzh_charcnt
-The number of bytes of timezone abbreviation strings
+The number of bytes of time zone abbreviation strings
 stored in the file.
 .RE
 .PP
 The above header is followed by the following fields, whose lengths
-vary depend on the contents of the header:
+depend on the contents of the header:
 .IP * 2
 .I tzh_timecnt
 four-byte signed integer values sorted in ascending order.
@@ -75,25 +73,29 @@ at which the rules for computing local time change.
 .IP *
 .I tzh_timecnt
 one-byte unsigned integer values;
-each one tells which of the different types of local time types
+each one but the last tells which of the different types of local time types
 described in the file is associated with the time period
-starting with the same-indexed transition time.
+starting with the same-indexed transition time
+and continuing up to but not including the next transition time.
+(The last time type is present only for consistency checking with the
+POSIX-style TZ string described below.)
 These values serve as indices into the next field.
 .IP *
 .I tzh_typecnt
 .I ttinfo
 entries, each defined as follows:
-.PP
-.in +4n
-.EX
+.in +.5i
+.sp
+.nf
+.ta .5i +\w'unsigned char\0\0'u
 struct ttinfo {
-    int32_t       tt_gmtoff;
-    unsigned char tt_isdst;
-    unsigned char tt_abbrind;
+	int32_t	tt_gmtoff;
+	unsigned char	tt_isdst;
+	unsigned char	tt_abbrind;
 };
-.EE
-.in
-.PP
+.in -.5i
+.fi
+.sp
 Each structure is written as a four-byte signed integer value for
 .IR tt_gmtoff ,
 in a standard byte order, followed by a one-byte value for
@@ -110,7 +112,7 @@ should be set by
 .BR localtime (3)
 and
 .I tt_abbrind
-serves as an index into the array of timezone abbreviation bytes
+serves as an index into the array of time zone abbreviation bytes
 that follow the
 .I ttinfo
 structure(s) in the file.
@@ -165,21 +167,26 @@ eight bytes are used for each transition time or leap second time.
 After the second header and data comes a newline-enclosed,
 POSIX-TZ-environment-variable-style string for use in handling instants
 after the last transition time stored in the file
-(with nothing between the newlines if there is no POSIX representation for
-such instants).
-The POSIX-style string must agree with the local time type after
-both data's last transition times; for example, given the string
+or for all instants if the file has no transitions.
+The POSIX-style TZ string is empty (i.e., nothing between the newlines)
+if there is no POSIX representation for such instants.
+If nonempty, the POSIX-style TZ string must agree with the local time
+type after the last transition time if present in the eight-byte data;
+for example, given the string
 .q "WET0WEST,M3.5.0,M10.5.0/3"
 then if a last transition time is in July, the transition's local time
 type must specify a daylight-saving time abbreviated
 .q "WEST"
 that is one hour east of UT.
+Also, if there is at least one transition, time type 0 is associated
+with the time period from the indefinite past up to but not including
+the earliest transition time.
 .SS Version 3 format
 For version-3-format timezone files, the POSIX-TZ-style string may
 use two minor extensions to the POSIX TZ format, as described in
 .BR newtzset (3).
 First, the hours part of its transition times may be signed and range from
-\-167 through 167 instead of the POSIX-required unsigned values
+\*-167 through 167 instead of the POSIX-required unsigned values
 from 0 through 24.
 Second, DST is in effect all year if it starts
 January 1 at 00:00 and ends December 31 at 24:00 plus the difference