The LAST_TOD field is, as the name states, an 8 byte Time of Day (clock) value. The only format available is .... TOD and this support different lengths but not much more customization.
If you want flexibility in formatting your time stamp, you could convert the LAST_TOD field to, e.g., DATETIME or SMFTIMESTAMP using
define last_smfstamp as convert(last_tod,tod,smftimestamp)
CONVERT is described here.
However, you can also extract just the DATE part of the timestamp:
define last_date as convert(last_tod,tod,date)
as this allows for a range of format, such as $date and eudate. Note, the defined fields cannot be used as statistics (MIN, MAX) in the SUMMARY command, so you keep using the TOD fields for summary. Also, the CONVERT function works on the input data, you cannot CONVERT the result of a summary statistic.