代码如下:
$smarty = new Smarty;
$smarty->assign('yesterday', strtotime('-1 day'));
$smarty->display('index.tpl');
index.tpl:
{$smarty.now|date_format}
{$smarty.now|date_format:"%A, %B %e, %Y"}
{$smarty.now|date_format:"%H:%M:%S"}
{$yesterday|date_format}
{$yesterday|date_format:"%A, %B %e, %Y"}
{$yesterday|date_format:"%H:%M:%S"}

输出代码如下:
Feb 6, 2001
Tuesday, February 6, 2001
:33:00
Feb 5, 2001
Monday, February 5, 2001
:33:00

常用格式：{$smarty.now|date_format:"%Y-%m-%d %H:%M:%S"}   显示2010-05-16 05:20:14

更多请参看smarty手册，下面只作简单几个介绍。。

%a - abbreviated weekday name according to the current locale
（根据当地格式输出“星期”缩写格式）
%A - full weekday name according to the current locale
（根据当地格式输出“星期”全称格式）
%b - abbreviated month name according to the current locale
（根据当地格式输出“月”缩写格式）
%B - full month name according to the current locale
（根据当地格式输出“月”全称格式）