The date at which the recompression treatment began. The only element inside <dateofrecompressiontreatment> is <datetime>.
<datetime>
(see also <dive>)
<repetitiongroup id="rep345">
<dive>
...
<hyperbaricfacilitytreatment>
<!-- start of recompression treatment -->
<dateofrecompressiontreatment>
<!-- Date February 4th, 1999 (Thursday) -->
<datetime>1999-02-04</datetime>
</dateofrecompressiontreatment>
<!-- here more statements -->
...
<hyperbaricfacilitytreatment>
</dive>
<!-- here can follow more dives -->
...
</repetitiongroup>