I am writing an email and wanted to refer to this coming Tuesday. The phrase "Tuesday est" popped into my mind (something Miss Marple might have said) but when I googled it I could find no reference. I have a feeling that 'est' isn't correct, but there is a word or I presume an abreviation that sounds like it that means next. Could you please tell me what it is?

Aha! I have just had a brain wave, it isn't 'est', it's 'inst'. Is that right? What does it stand for?