Do you know about the Iranian Feast of NowRuz? It’s the Persian New Year, and falls on March 21. Now means new and ruz means day, so NowRuz means new day. Here we know it as the vernal equinox and the start of springtime. In Iran, it’s also a pre-Muslim holy day for Zoroastrians, a day when Iranian families visit each other and talk about what they hope to see in the new year.

It would be a good opportunity for President Trump to mark a new day in US-Iran relations — one that corrects his predecessor’s poor treatment of the Iranian people.

March 21, 2017, will be the 38th NowRuz since the 1979 fall of the shah and the Khomeinist revolution. How cruel the promise of a happy new year must have seemed during all those years!

Have you seen photos from pre-Khomeini Iran? They’re heartbreaking. They show women fashionably dressed in the city or in bathing suits at the beach, boys and girls together on the sidewalks of Tehran.

Iranians who conducted themselves like that today would be busted by the country’s morality police. They’re everywhere. Some of its members are simply volunteer busybodies, some are looking for the perks the regime has to offer — college slots for their kids, government jobs, bank loans. At NowRuz they’ll be out in force, to police those doffing winter coats to greet the sun.

Iranian President Hassan Rouhani has criticized the morality police but hasn’t reined them in. Last year at this time, the regime announced that an additional 7,000 undercover officers would patrol the streets to arrest women who had too much hair showing from under a headscarf or were out walking with a boyfriend.

For criticizing the morality police, Rouhani was slapped down by Supreme Leader Ayatollah Ali Khamenei, the man the morality police answer to, and that’s put Rouhani on the defensive. He’s up for re-election on May 19, and it’s by no means a sure thing. He is opposed by several hardliners, and in any event the possibility of real liberalization is constrained by the real powers in Iran: the Iranian Revolutionary Guard Corps.

That’s why change will come to Iran, if at all, from the streets, from an Iranian Spring. And the Iranians who want to rid their country of its oppressive regime must be told that America shares their goals. Unlike the Arab Spring movements in Egypt and Libya, an Iranian Spring would replace an implacable foe of the United States with a more liberal and pro-Western government.

Elsewhere, Arab Spring movements replaced friendly governments in Egypt, or defanged ones in Libya, with the anti-American Muslim Brotherhood in Egypt and the Islamic jihadists who killed our ambassador to Libya. Those were the kinds of uprisings President Barack Obama and Hillary Clinton supported.

That was American foreign policy over the last eight years. For our friends — betrayal. For our enemies — submission.

What Obama and Hillary didn’t support were the street protests in Tehran after Mahmoud Ahmadinejad won the presidency in 2009. Tens of thousands of people marched down the streets of Tehran shouting “Down with dictatorship!” while fighting running battles with the Revolutionary Guards. Obama’s response was a tepid statement that it’s “up to Iranians to make decisions about who Iran’s leaders will be,” and that “we respect Iranian sovereignty and want to avoid the United States being the issue inside of Iran.”

By contrast, an Obama spokesman supported the Tahrir Square protesters in Egypt even before the Mubarak government fell.

It’s time to show our solidarity with the people of Iran. With Obama in office, we sided with one of the world’s greatest human-rights abusers, but they no longer have a friend in the White House.

I have a suggestion for Trump. After we ignored the street protests against the Iranian dictatorship, after we cut our disastrous Iran deal, after we abandoned Israel to the threat of medium-range missiles from the Iranian Revolutionary Guards, after American hostages were allowed to rot in Iranian jails, let the president welcome NowRuz with a message to the Iranian people.

Let him wish them a happy and prosperous new year, and the freedom that all men deserve from their cruel oppressors.

F.H. Buckley teaches at Scalia Law School. His most recent book was “The Way Back: Restoring the Promise of America.”