Date and Time in WordPress:

<p>Posted: <?php the_time(‘F j, Y’); ?> at <?php the_time(‘g:i a’); ?></p>

By <?php the_author(); ?> on <?php the_date(‘F j, Y’); ?>

Modified or Updated:
Modified <?php the_modified_date(); ?>

Reference:
=================

Day of Month
d	Numeric, with leading zeros	01–31
j	Numeric, without leading zeros	1–31
S	The English suffix for the day of the month	st, nd or th in the 1st, 2nd or 15th.
Weekday
l	Full name (lowercase ‘L’)	Sunday – Saturday
D	Three letter name	Mon – Sun
Month
m	Numeric, with leading zeros	01–12
n	Numeric, without leading zeros	1–12
F	Textual full	January – December
M	Textual three letters	Jan – Dec
Year
Y	Numeric, 4 digits	Eg., 1999, 2003
y	Numeric, 2 digits	Eg., 99, 03
Time
a	Lowercase	am, pm
A	Uppercase	AM, PM
g	Hour, 12-hour, without leading zeros	1–12
h	Hour, 12-hour, with leading zeros	01–12
G	Hour, 24-hour, without leading zeros	0-23
H	Hour, 24-hour, with leading zeros	00-23
i	Minutes, with leading zeros	00-59
s	Seconds, with leading zeros	00-59
T	Timezone abbreviation	Eg., EST, MDT …
Full Date/Time
c	ISO 8601	2004-02-12T15:19:21+00:00
r	RFC 2822	Thu, 21 Dec 2000 16:01:07 +0200