How to to convert from ldap time format to js date format?

Question

I want to read a time stamp from Active Directory and compare it to an other date created in JS. From AD I'm getting the date in form of an 18-digit number (time in 100 nanoseconds since Jan 1, 1601 UTC). JavaScript uses date numbers in form of a 13-digit number (time in miliseconds since Jan 1, 1970 UTC).

Is there a convert function already implemented or how would you convert it?

Answer 1

Based on the question here*, 1.29265206716E+17 represents 2010-08-17T12:11:11Z so that can be used as a test value. The LDAP time value is in units of 0.0000001 of a second, whereas ECMAScript uses 0.001 of a second.

So the steps are:

1. Convert the LDAP time value to milliseconds (divide by 1e4)
2. Get the time difference between 1601-01-01 and 1970-01-01 in milliseconds
3. Subtract the difference
4. Pass to the Date constructor to create a Date object

Which can be combined into a single expression:

function ldapToJS(n) {

  // Longer, equivalent to short version
  // return new Date(n/1e4 + new Date(Date.UTC(1601,0,1)).getTime());

  // Shorter, more efficient. Uses time value for 1601-01-01 UTC
  return new Date(n/1e4 - 1.16444736e13);
}

console.log(ldapToJS(1.29265206716E+17).toISOString()); // 2010-08-17T02:11:11.600Z
console.log(ldapToJS(1.3160237812e17).toISOString());   // 2018-01-12T13:36:52.000Z

function doConversion(){
  document.getElementById('dateString').textContent = ldapToJS(+document.getElementById('ldap').value).toISOString();
}

<input placeholder="LDAP time value" id="ldap">
<button onclick="doConversion()">Convert</button>
<br>
<span id="dateString"></span>

LDAP timestamps can be generated and converted to date strings at the LDAP, Active Directory & Filetime Timestamp Converter.

* How to convert LDAP timestamp to Unix timestamp

You could even add a static fromLDAPTV method to the built-in Date:

// Convert LDAP time value to Date
if (!Date.fromLDAPTV) {
  Date.fromLDAPTV = function (n) {
    return new Date(n/1e4 - 1.16444736e13);
  }
}

console.log(Date.fromLDAPTV(131602386750000000))

// Convert LDAP string to date (only timezone Z)
if (!Date.fromLDAPString) {
  Date.fromLDAPString = function (s) {
    var b = s.match(/\d\d/g);
    return new Date(Date.UTC(b[0]+b[1], b[2]-1, b[3], b[4], b[5], b[6]));
  }
}

console.log(Date.fromLDAPString('20180112232359Z'));