With Parliament usually dissolved within two months of the release of the boundaries report in past elections, observers expect the custom to hold.

Sept 12 remains the hot date for the polls - Seventh Month celebrations notwithstanding. This is the last Saturday of the week-long school holidays, and schools are typically used as polling stations.

School examinations rule out October and early November as windows for an election, and late November will be packed with global summits involving Prime Minister Lee Hsien Loong and other ministers.

Another popular date, Sept 5, is no longer viable as Parliament should have been dissolved last Wednesday for that to be the case.

The stage looks set: changes to the electoral boundaries were announced late last month, National Day is over, and PAP organising secretary Ng Eng Hen has gone on to declare "we are in election season".

The Elections Department on Thursday announced several changes to election regulation, including the printing of candidates' photos on the ballot slip. This sorting out of the "nitty-gritty", observers say, sends the strongest signal yet that elections will come soon.

The ruling party, observers point out, stands to benefit from calling the elections - which must be held by January 2017 - sooner rather than later. With the swell of national pride after National Day, and outpouring of grief over the death of founding Prime Minister Lee Kuan Yew, who would have turned 92 on Sept 16, the ground looks sweeter than ever for the PAP, whose vote share took a tumble in the last polls.

Political science professor Bilveer Singh from the National University of Singapore believes it makes no sense for the PAP to hold off when a September election is "a very good window to go to the polls and win big".

"Any delay will eventually hurt the ruling part as the opposition would be more prepared, and public goodwill will start to dissolve," he says.