ISO
8601:2000(E)
©
ISO
2000
All
rights
reserved
17
If
the
time
of
the
day
is
represented
in
basic
format
in
a
context
that
does
not
clearly
identify
a
time
only
expression,
the
time
designator
[T]
shall
be
used
immediately
in
front
of
the
presentations
defined
in
5.3.1.1
through
5.3.1.3.
5.3.2
Midnight
The
complete
representations
in
basic
and
extended
format
for
midnight,
in
accordance
with
5.3.1,
shall
be
expressed
in
either
of
the
two
following
ways:
Basic
format
Extended
format
a)
000000
00:00:00
(the
beginning
of
a
day);
b)
240000
24:00:00
(the
end
of
a
day).
The
representations
may
be
reduced
in
accordance
with
5.3.1.2,
truncated
in
accordance
with
5.3.1.4
or
designated
to
be
a
time
expression
in
accordance
with
5.3.1.5.
To
represent
midnight
the
representations
may
be
expanded
with
a
decimal
fraction
containing
only
zeros
in
accordance
with
5.3.1.3.
NOTE
1
Midnight
will
normally
be
represented
as
[0000]
or
[2400].
NOTE
2
The
choice
of
representation
a)
or
b)
will
depend
upon
any
association
with
a
date,
or
a
time-interval.
Representations
where
[hh]
has
the
value
[24]
are
only
preferred
to
represent
the
end
of
a
time-interval
in
accordance
with
5.5.1.
NOTE
3
The
end
of
one
day
[2400]
coincides
with
[0000]
at
the
start
of
the
next
day,
e.g.
2400
on
1985
April
12
is
the
same
as
0000
on
1985
April
13.
If
there
is
no
association
with
a
date
or
a
time-interval
both
a)
and
b)
represent
the
same
clock
time
in
the
24-hour
timekeeping
system.
5.3.3
Coordinated
Universal
Time
(UTC)
To
express
the
time
of
the
day
in
Coordinated
Universal
Time,
the
representations
specified
in
5.3.1.1
through
5.3.1.3
shall
be
used,
followed
immediately,
without
spaces,
by
the
UTC
designator
[Z].
The
examples
below
are
complete
and
reduced
precision
representations
of
the
UTC
time
20
minutes
and
30
seconds
past
23
hours:
Basic
format:
hhmmssZ
EXAMPLE
232030Z
hhmmZ
2320Z
hhZ
23Z
Extended
format:
hh:mm:ssZ
EXAMPLE
23:20:30Z
hh:mmZ
23:20Z
not
applicable
5.3.4
Local
time
and
Coordinated
Universal
Time
5.3.4.1
Difference
between
local
time
and
Coordinated
Universal
Time
When
it
is
required
to
indicate
the
difference
between
local
time
and
UTC,
the
representation
of
the
difference
can
be
expressed
in
hours
and
minutes,
or
hours
only.
It
shall
be
expressed
as
positive
(i.e.
with
the
leading
plus
sign
[+])
if
the
local
time
is
ahead
of
or
equal
to
UTC
and
as
negative
(i.e.
with
the
leading
minus
sign
[])
if
it
is
behind
UTC.
The
minutes
component
of
the
difference
may
only
be
omitted
if
the
time
difference
is
exactly
an
integral
number
of
hours.
Basic
format:
±
hhmm
EXAMPLE
+0100
±
hh
+01
Extended
format:
±
hh:mm
EXAMPLE
+01:00
