By default the current day is highlighted. To highlight (an)other day(s) use cw and cdow. cw gives the week and cdow the day of the week to be highlighted.
Together they determine a specific day to be highlighted.
cw alone will highlight the whole week.
cdow alone will highlight the given weeek day for the whole month.
A given month of this year can be specified with 1 like this {{ISOCALENDAR|August}}. Alternatively m can be used e.g. {{ISOCALENDAR|m=Sep}}. Perhaps you want a different title e.g. {{ISOCALENDAR|This November|m=11|y=2006}}.
A given month and year can be specified with 1 like this {{ISOCALENDAR|May 2006}}. Alternatively m and y can be used e.g. {{ISOCALENDAR|m=June|y=2006}}. Perhaps you want a different title e.g. {{ISOCALENDAR|Quintilis MMVI|m=5|y=2006}}.
You can highlight Saturday of week 3 in January 2021 using {{ISOCALENDAR|January 2021|cw=3|cdow=Sat}}. You can highlight all of week 6 in February 2021 using {{ISOCALENDAR|February 2021|cw=23}} You can highlight all Thursdays of March 2021 using{{ISOCALENDAR|March 2021|cdow=4}}
