There are two calendars at the White House these days. The first measures the tenure of the president as prescribed by the Constitution. It shows 210 weeks left. The second reflects the time insiders think he really has to accomplish his major domestic policy goals. It runs out before the end of 1985.

Why the rush? In part it may be that so many of the senior White House aides think of themselves as short-timers. Counselor Edwin Meese III is awaiting confirmation as attorney general. Chief of Staff James A. Baker III is increasingly impatient to find a major Cabinet post for himself. Deputy chief of staff Michael K. Deaver wants to quit after the Inaugural ceremonies to make money as a public relations man.

Baker's policy deputy, Richard Darman, would like to leave, too, for a job involving foreign economic policy. Budget director David Stockman, whose first child is expected this spring, is also eager to expand his income in the private sector, after this year's bruising budget battle.

But there is more to the sense of urgency than just the personal timetables of the senior Reagan aides. There is also the hunch on the domestic side of the administration that, after 1985, Ronald Reagan will increasingly focus his energy -- and seek to make his mark -- in foreign policy. The lure of an arms-contral summit with the Soviet leaders is a powerful one: A man who has won two landslide victories for president has little left to spur his ambition than the Nobel Peace Prize.

For all these reasons and more, the White House wants a fast start on the key measures in the domestic program -- the deficit-reduction package and tax reform -- once the Inauguration is out of the way. But managing the whole project will test the skills of the team of Reagan aides as never before. The tax-simplification proposal, which Reagan has yet to endorse in anything more than concept, must be put into final form in a fashion that commands sufficient bipartisan support so that it appears to have a plausible chance of enactment.

Without a credible tax simplification and rate-reduction plan, Reagan will have little to offer domestically but the pain of his budget cuts. Republicans in the House and senators facing reelection next year abhor the role of Scrooge almost as much as Reagan does.

But here's the rub. The only way the White House can foresee uniting the GOP on the budget is to force Congress to deal with the spending side of the proposal before any decisions are made on revenue levels. Otherwise, there will be a fatal split between Senate Republicans, many of whom prefer higher taxes to severe domestic program cuts, and House Republicans, most of whom are set against tax hikes.

Even addressing the spending cuts first does not begin to solve the political problem, for there is widespread recognition in the White House that the budget decisions the president made in December will not survive scrutiny as they stand on Capitol Hill.

Having failed to force Secretary of Defense Caspar Weinberger to accept the Pentagon's prescribed share of the spending reductions for future years, there are those in the administration who would like to make Weinberger -- rather than Stockman or the president -- spend his political capital defending the budget proposal in Congress. Their not-so-secret hope is that Weinberger and his budget will both be cut down to size by Congress -- and soon.

Once the Capitol Hill political proc determined a realistic defense budget figure, they say, it might be possible -- but still not easy -- to bargain for a set of domestic spending reductions that would share the pain equitably. This would permit a solid phalanx of Republican senators and a handful of conservative Democrats to pass a budget reolution -- or at least the spending targets portion.

Until that happens, they concede, there is no way to force the Democratic leadership of the House to give the president a vote on a similar package. Delay in the Republican Senate, they acknowledge, means defeat in the Democratic House. Once a spending package passes the Senate, however, the president can take to the airwaves and the campaign trail demanding action in the House.

But at this point, it is not even certain that Republican senators -- the first vital allies the president needs -- will go along with him, for the budget cuts Reagan is proposing go to the heart of the Republican constituency. Farmers, small business operators, veterans, realtors, developers, exporters -- to say nothing of the middle-class beneficiaries of Medicare -- are all targets of this year's spending cuts.

Given the difficulty of the task ahead, you can underestand the urgency of a quick start. And you can also understand why some of the president's men are looking for an early exit.