If plants are heeled-in during this fecund time slot, gardeners will be blessed with much fruit.
Any day either side of the weekend is forbidden.
Today at least for most of us the holiday has all but lost any political nuance.
In fact, there's some irony that it's not mandatory (unlike Easter, Anzac and Christmas) for shops to close on the very day that celebrates workers' rights.
We can only guess as to what the holiday's founder, carpenter Samuel Parnell (who successfully argued for the eight-hour day) would feel about the tomato symbolising a day he sweat blood to establish. One also wonders - now that the nation spends more time than ever in its work trousers - why the holiday hasn't been extended at a commensurate level.
To you poor sods working today, make sure you plant your tomatoes before tonight's witching hour.