C# (.NET Core), 55 54 bytes

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Saved 1 byte thanks to Shaggy

()=>{var k=0;k=System.DateTime.Now.DayOfWeek>0?0:1/k;}

Lucky that Sunday is indexed 0 in enum or else it would've needed to be (System.DayOfWeek)7

C# (.NET Core), 55 54 48 bytes

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Saved 1 byte thanks to Shaggy

Saved 5 byte thanks to Emigna

Saved 1 byte thanks to Kevin Cruijssen

_=>{var k=1/(int)System.DateTime.Now.DayOfWeek;}

Lucky that Sunday is indexed 0 in enum or else it would've needed to be (System.DayOfWeek)7

C# (.NET Core), 55 bytes

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()=>{var k=0;k=System.DateTime.Now.DayOfWeek==0?1/k:0;}

Lucky that Sunday is indexed 0 in enum or else it would've needed to be (System.DayOfWeek)7

C# (.NET Core), 55 54 bytes

Try it online!

Saved 1 byte thanks to Shaggy

()=>{var k=0;k=System.DateTime.Now.DayOfWeek>0?0:1/k;}

Lucky that Sunday is indexed 0 in enum or else it would've needed to be (System.DayOfWeek)7