Why do you say 1788/9? Weren't the popular elections held on the same day?
The Constitutional Convention was a bit irregular. They were only supposed to be proposing amendments to the Articles of Confederation. They didn't want to completely bypass the Continental Congress, so they had George Washington, who was presiding officer of the convention, send the proposed Consitution to the Congress and request that they forward it to the people of the 13 States for their consideration (the ratifying conventions in the States bypassed the legislatures). The Congress was also asked to trigger the start up of the government in event that the Constitution was ratified by 9 States.
The Constitution was proposed in September 1787 and by the summer of 1788, 9 States had ratified the Constitution. The Continental Congress the first Wednesday in March, 1789 as the day that the Congress would meet. It set the first Wednesday in February, 1789 for the electors to meet in their respective States to cast their electoral votes., and it set the First Wednesday in January, 1789 for the electors to be chosen. So as it turns out, the electors for the first election were chosen in 1789. Some sources date the election as 1789, while the one I was using used 1788/89. I don't know whether this was to maintain the pattern of an election every 4 years, or whether some states actually chose their electors in 1788.
Congress (under the Constitution) first met on the first Wednesday in 1789 which happened to be the 3rd of March. It took a while before there was a quorum in both Houses. As soon as that happened, they could meet in joint session and count the electoral votes (and if necessary choose the President). It took some time for Washington to get to New York City (where Congress was meeting) so he was not sworn in until June of 1789.
The Constitution does not specify any dates, so Congress made the interpretation that terms of office for both Congress and the President begin on March 3rd. If a 2 year term started on the March 3rd, then the following term started on March 3rd. To avoiid the pitfalls of not having a President chosen by the start of his term, Congress set out the practice of the outgoing, lame duck Congress counting the electoral votes and choosing the President if necessary.
The schedule had to provide time for Congress to meet in February, time for the tally of the electoral votes to be sent from each state to the capital, time for the electors to travel to the meeting place in their respective states, and time to count and canvass the votes for electors. This resulted in subsequent popular elections being held in November of the even year preceding the start of the presidential term. Initially, Congress did not set a specific date but simply set time windows. It wasn't until 1848, that Congress set a uniform election date of the 1st Tuesday after the 1st Monday in November. A uniform date for election of Congress did not happen until after the Civil War (the variation was much greater).
Yes.