The notion of the "First 100 Days in Office" was first mentioned by the United States’ 32nd President Franklin Delano Roosevelt in July 1933. He was serving the first of his four terms in office and the country was in post-Depression crisis, writes Washington Correspondent Caitríona Perry.
He proposed and Congress enacted a massive recovery programme, leading him to praise the achievements of the "the first 100 days".
Since then it has become a popular, if at times almost meaningless, way of holding new presidents to account.
The thinking being there is a period of goodwill, and vigorous activity before grudges form and the Congressmen and women start thinking once again once again of re-election.
Before the 2016 Presidential Election, last October, Donald Trump launched his 100 day action plan. He called it 'Donald Trump’s Contract with the American People'. You can read it here.
It is just a two page document but does contain ten pieces of legislation he had hoped to get passed through Congress. On election night that might have seemed ambitious but not completely unachievable, given that Republicans had control of both Houses of Congress and the Presidency.
However since he swore the oath of office to being the 45th President, those expectations have been managed downwards.
While the pace of activity has been at times frenetic, real concrete achievements have so far been few and far between.
President Trump himself, despite launching that 100 day action plan, has downplayed the value of the benchmark in recent days, presumably because as a businessman who previously judged himself and his employees based on targets achieved, the portfolio does not look so good this time.
In a rather telling, and circumspect interview with Reuters, published today, President Trump says: "I loved my previous life. I had so many things going.
"This is more work than in my previous life. I thought it would be easier."
But this is not a family business, although it might be staffed by close family and friends, and the President alone has limited power. The founding fathers purposely designed it that way.
Mr Trump made many campaign promises, but there were ten pretty core ones:
(1) Repeal and Replace Obamacare:
The number one piece of legislation that Mr Trump and many other Republicans promised to pass upon taking office, was a law to repeal and replace Obamacare; former US President Barack Obama’s legacy - the Affordable Healthcare Act.
That failed at the first pass, and a second attempt to put it to another vote has also been called off.
Speaker Paul Ryan, the most senior Republican in Congress saying they just do not have the votes, and rather than risk a fail, they are not voting on it at all.
(2) Deport illegal immigrants.
Next up a sworn promise to deport two million illegal immigrants within his first hours in office ... that has not happened but he has signed executive orders beefing up the numbers of immigration officers, and the powers available to them.
He has signed an executive order, that is currently stalled as a result of a court order, that would remove funding to so-called ‘sanctuary cities’ - areas where the authorities turn a blind eye to their undocumented populations as long as they are otherwise law-abiding.
So while President Trump has not deported two million, there has been a reported increase in the number of raids and deportations.
(3) Build a Wall; get Mexico to pay for it.
Mr Trump’s signature promise to ‘Build a Wall and have Mexico’ pay for it ... that has met a wall of resistance from many quarters, Democrats and Republicans, even some border control agents, and many of those living along the border.
The issue of who would pay for it even threatened to shut down the US Government tonight when a funding deadline is due to expire. President Trump withdrew the requirement to find taxpayer money to fund it to remove the risk of shutting down the US government on the eve of his 100th day in office.
And although it is not clear where the money will come from, President Trump was this week resolute when he told reporters at a photo opportunity at the White House "the wall will get built".
(4) The Travel Ban
During the campaign this was first touted as a ban on Muslim immigrants, but that was softened to be immigrants from Muslim-majority countries with terrorist links.
When Mr Trump got into office, on legal advice, it became a temporary ban on immigrants from countries that were already on a US ‘watch list’.
The ‘travel ban’ also sought to bar refugees from across the world, with an extra penalty for Syrian refugees in the first iteration.
That first executive order was put on hold by a court, and upheld on appeal, so the President issued a second order to replace it. That too has been stalled by legal actions and court orders so the status quo remains.
(5) Jobs! Jobs! Jobs!
Another catch call from Mr Trump’s election rallies. He resonated with voters in lower-income areas, and particularly in the so-called rustbelt with his promise of economic advancement, and a pledge to "Bring Back the Jobs"! Jobs long lost to technology and globalisation.
While some car manufacturers and others have pledged to increase the number of jobs, and open extra factories here, many had said they had planned to do that anyway.
On the White House website, President Trump is claiming to have created 500,000 jobs since taking office.
He is quoting the US monthly jobs reports, but cannot strictly claim all of the credit as the January figures refers to most of Obama’s last few weeks. Counting February and March, gives an average gain of 158,500, the average monthly gain for President Obama’s last full year was 187,000.
(6) Tax Reform
Another major promise to reform the US tax code. Just this week his Treasury Secretary Steve Mnuchin and National Economic Director Gary Cohn outlined a one page tax reform wish list.
There were so little details; nothing on income bands for example so it is hard to say just what is in store for working Americans.
The existing seven income tax bands will be reduced to three, and the well-flagged massive cut to corporate tax from 35% to 15% will go ahead.
So he has announced his rough blueprint, now the hard work starts, costing it and turning it into legislation that can pass through Congress.
(7) End Trade Deals
This was another huge part of the reason so many low and middle income workers were attracted to Mr Trump.
Many view trade deals, in particular the North American Free Trade Agreement as the root cause of many of their employment and general economic problems.
Mr Trump has pledged to withdraw from the Trans Pacific Trade Agreement.
Just this week, he almost launched a trade war with Canada and threatened to end NAFTA immediately, instead renegotiations are beginning.
(8) Appoint a Supreme Court Justice
This point was of particular importance to conservative voters during the election. Mr Trump said he would appoint a conservative judge as soon as he could, and he did just that.
Neil Gorsuch was sworn in as the newest member of the Supreme Court earlier this month.
Although Senate Republicans did have change the rules to get his confirmation passed.
(9) Defeat ISIS
It is far too soon to weigh this one up, but President Trump has been flexing US military muscle in recent weeks.
First he bombed a Syrian airfield in response to the chemical weapon attack which US intelligence sources claim was ordered by Syrian President Assad.
Then the US military dropped the biggest non-nuclear bomb in its arsenal in Afghanistan, on a site believed to house fighters of the ISIS-Khorasan group, an affiliate of the so-called Islamic State.
(10) Label China a currency manipulator
Another favourite tale of MrTrump’s at campaign rallies was about how the US was "losing" to China, and he was going to declare China a "currency manipulator".
That has not happened, and more so President Trump and Chinese President XI Jinping appear to have become allies, and possibly even friends.
Mr Trump hosted Xi at his Mar-a-Lago home in Florida and the pair are in close contact currently as they work to combat the threat posed by North Korea as it scale up its nuclear capabilities.
It has been a fast-paced and action packed first 100 days. In addition to the items listed above, President Trump has hosted 17 world leaders, including Taoiseach Enda Kenny.
He has signed 28 bills into law, and 30 executive actions so far (it is still only day 99).
He lost his National Security Advisor Mike Flynn, as investigations continue into Russian interference in the US election and specifically into connections with the Trump campaign.
President Trump has not yet made any overseas trips, but he has paid 33 visits to Trump-owned properties.
While his popularity ratings on starting the job were the lowest for any incoming President ever, and have not significantly changed, a raft of opinion polls released by the US media this week show that the Trump supporters, the ‘Silent Majority’ who put him in the White House are standing by him, and are pleased with the job that he is doing.
So for President Donald John Trump, it is a case of 99 days down, 1,362 to go.