 <p>Umm... I'm either missing something extremely obvious or everyone else is.</p> <p>You want to date operations? Use <code>to_date</code> and <code>to_char</code>. I'm going to assume this <code>ss:sss</code> means, seconds, then fractional seconds. You date appears to be a string so we need to convert it twice:</p> <pre><code>update b set first = to_char( to_date( my_date, 'yyyy/mm/dd-hh:mi:ss:ff3') ,'yyyy-mm-dd hh:mi:ss' ) </code></pre> <p>Generally, when using dates it's far, far easier to only use <a href="http://psoug.org/reference/date_func.html" rel="nofollow">date functions</a> and the provided <a href="http://ss64.com/ora/syntax-fmt.html" rel="nofollow">formats</a>.</p> <p>As an added point if you have a date, store it as a date. It'll save a world of bother later on.</p>