The next time someone tells you, ''There's no time like the present,'' ask them what day they had in mind.

Researchers reported recently that a study of heart attack patients in New Jersey revealed that those who arrived at hospitals on weekends were less likely to receive aggressive treatment and were more likely to die. So, though you can't plan on having a heart attack, you can plan on what might happen when you do. But what about going to the theater? Flying or having a baby? Being arrested? Every topic has its ''worst'' day watch. Woe to the autumn auto buyer, when rebates are few. Or the air traveler in June, when storm clouds gather.

The worst, by default, steals a look at the best. So stand what you learn next on its head.