You can change the length of time that the SMSC keeps a message and tries to deliver it. (Often the default value is 72 hours.) For a message sent to an emergency worker, for example, you might want to specify a very short validity period (such as 15 minutes). To change this value, include a validityPeriod field in the Data parameter of a SendGatewayMessage function or the return variable of the CFC listener method. To specify a time period, use the following pattern: YYMMDDhhmmsst00R. In this pattern, t indicates tenths of seconds, and 00R specifies that this is a relative time period, not a date-time value. The time format 00001063000000R, for example, specifies a validity period of 0 years, 0 months, 1 day, 6 hours, 30 minutes.