====== offsetDate ======
~~NOTOC~~
<WRAP right box>
== Syntax ==
  string|bool ADOConnection::offsetDate( 
         float $offset
         optional string $isoDate
  )
</WRAP>

===== Description =====
The function ''offsetDate()'' returns a string with the native SQL functions to calculate future and past dates based on ''$isoDate'' in a portable fashion. If ''$isoDate'' is not defined, then the current date (at 12 midnight) is used. 

The function returns the SQL string that performs the calculation when passed to ''Execute()''. The value returned when the statement is executed is an //**ISO Date**//. 

The function returns false if invalid parameters are provided.

<WRAP info>
Passing a decimal offset less than one without 
specifying a base date will always return the 
current date because the calculation time 
basis is always the beginning of the current date
</WRAP>

===== Inputs =====
The $offset is the number of days that should be added or subtracted from the reference date; the decimal portion is the fraction of a day (e.g. 0.5 = 12 hours)

The $isoDate can be:
   * A basis date in ISO format including a time portion, if a fractional calculation is required
   * An SQL statement that produces an ISO date
   * An SQL column if the method is to be used to calculate date offsets based on table values
   * skipped or false for today

===== Examples =====

Get date one week from now

<code php>
$fld = $conn->OffsetDate(7); 
/*
 * returns "(trunc(sysdate)+7")
 */
</code>

Oracle: get date and time that is 60 hours (2.5 days) from current

<code php>
$fld = $conn->OffsetDate(60/24, $conn->sysTimeStamp); 
/*
 *   returns "(sysdate+2.5)"
 */  

$conn->Execute("UPDATE TABLE SET dodate=$fld WHERE ID=$id");
</code>

SQL Server: Get Date -273.5 Hours in the past

<code php>
$fld = $db->offsetDate(-273.5/24);

/*
 * Returns " SELECT FORMAT(DATEADD(hour ,-273.5,GETDATE()), 'yyyy-MM-dd')"
 */
</code>

Generating A Date From a column Value. 
In this example we would use the statement to return a date 7 days forward from the current value of the column "delivery date".

<code php>
$newDeliveryDate = $db->offsetDate(7, 'delivery_date');

$SQL = "SELECT $newDeliveryDate 
          FROM delivery_master";         
</code>