The source does not provide a date of publication. The date used here is the access date.

TIV (trend-indicator value) is a unit invented by SIPRI. It is used to allow comparison between the data on deliveries of major conventional weapons and to identify general trends.
The TIV is based on the known unit production costs of a core set of weapons and is intended to represent the transfer of military resources rather than the financial value of the transfer.
For further information please refer to the SIPRI explanation of TIV.