Issue with Is Null

Hi,

Can anyone assist with the IsNull part of this formula which is returning a syntax error of "Expecting )" at the first comma.

var TimeOfDay TOD = [Interaction Time];

If(
$TOD > ToTimeOfDay("12:01am") and $TOD <= ToTimeOfDay("12:00pm"), "Morning",
$TOD > ToTimeOfDay("12:00 pm") and $TOD <= ToTimeOfDay("5:00 pm"), "Afternoon",
$TOD > ToTimeOfDay("5:00 pm") and $TOD <= ToTimeOfDay("12:00 am"), "Evening",
IsNull($TOD ,"", "Other")

Thanks,

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Tim Egerton
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