Jan. 1 is Mohamed Abdulmunem's birthday. His wife Dima's, too. Same for his two eldest children, Abdulkerim and Lim.

A week before the big day, they had already planned the menu for the celebration in their apartment in Mississauga – favourites from their native Syria, including kibbeh (meat croquettes), chicken and peas and a spread of 16 desserts such as chocolate biscuits and cake.

This is the first time the Abdulmunems will celebrate their matching birthdays together – and, they hope, the last.

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Not one of them was actually born on Jan. 1. The were assigned the identical dates of birth after they fled their town of Jisr al-Shughur in northwestern Syria and registered as refugees in Turkey in 2014. When they arrived in Canada in September, the dates on their papers from Turkey were carried over to all the forms they filled out in their new home.

Explaining his frustration to a reporter through a translator, Mr. Abdulmunem pulled out a bundle of documents from his jacket.

Among them were his family's Ontario health cards, all with the purple trillium icon on a mint-coloured background – and "01 – 01" listed as the month and day of birth. That mistake is repeated on their permanent resident cards, their landing papers and Mr. Abdulmunem's driver's licence. (Only the youngest child's date of birth is listed correctly, because the child was born in Turkey.)

This is the fate of many refugees who arrive in Canada. As a result of not knowing their own date of birth or not having access to government documents, refugees are often assigned Jan. 1 as a birth date by agencies or governments they came into contact with before reaching Canada.

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Immigration, Refugees and Citizenship Canada does not keep track of such data, but settlement workers estimate there could be thousands of immigrants in Canada who have Jan. 1 listed as their birth date without actually being born on that day.

For some, it's a trivial matter – one they're only reminded of when filling out forms. But for others, especially those who know their true birth date but may not have the documents to prove it, being assigned a date arbitrarily can bring on myriad complications when it comes to accessing public benefits or travelling out of Canada.

It is global practice for the United Nations High Commissioner for Refugees (UNHCR) to assign Jan. 1 to those who do not know their date of birth. This is commonly done in intermediary countries where refugee claimants stay, sometimes in camps, before they settle in Canada.

Until about a year ago, if Canadian immigration officers were processing a refugee who did not know their date of birth, they would estimate the birth year and use the refugee's interview date as the birth month and day. But since Jan. 16, 2015, they have been instructed to use an asterisk for any unknown portions of the date of birth. If a refugee holds travel documents from any country listing their birth date – including Jan. 1 – Canadian officials fill out the forms using that date.

In many countries, births are not recorded because of low literacy rates or because civil or birth registration systems don't exist, said Ottawa-based UNHCR spokeswoman Gisèle Nyembwe in an e-mail. She said this is particularly the case with refugees from Somalia and Afghanistan, the Rohingya minority from Myanmar, Darfuri Sudanese and many West African populations. If they are from a rural region or unstable environment, refugees may not even know their year of birth.

"Sometimes they would associate it with an event or incident that happened. For example, the year when the fighting started or the year when the revolution started," said Saleem Spindari, the manager of refugee support services at MOSAIC, a Vancouver settlement organization.

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But on occasion, refugees may know their birth date but are assigned the wrong one because their identity documents have been lost or destroyed.

Mr. Spindari says an assigned birth date may have negative consequences many years later. If someone wants to travel back to their home country but the date of birth on their old documents doesn't match their new one, they could be denied entry – a concern Mr. Abdulmunem has if his hometown is ever deemed safe again. If a child is actually under 18 but her documents say she is older, her parents could be denied the federal child benefit. And a child may not be eligible to go to school if his date of birth is listed erroneously.

If newcomers have incorrect information listed on Canadian government-issued documents and have valid identification to prove the errors, they can submit changes on the Immigration, Refugees and Citizenship Canada website, said department spokeswoman Johanne Nadeau.

If only it had been that simple for Bara-a Mubarak Salim. In 2000, Ms. Salim, then just four years old, travelled with her Darfuri family from Sudan, where life was difficult and dangerous, to Egypt, where it wasn't much better. Her family did not have access to their birth certificates, so the UNHCR registered them all – with the exception of her father – with Jan. 1 birth dates. The error, compounded by incorrect birth years, followed them to Canada after they arrived in Vancouver as refugees in 2004.

They were eventually reunited with their Sudanese birth certificates, but countless attempts to work with settlement agencies and government case workers to get their real identities recognized on their new documents hit roadblock after roadblock. Ms. Salim is still waiting to hear from the immigration department after submitting papers to them in the summer.

"Sometimes even people when they see my ID they're, like, 'What?!' I have to explain it to everybody all the time – even at school, even to my teachers," she said. "I couldn't go with something that wasn't right."

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Her year of birth is also off by two years on her ID, so Ms. Salim had to bring her birth certificate to school so she would be allowed to graduate.

To some degree, her younger sisters accepted their new identities – life was simpler that way. When they were younger, they would celebrate their birthdays – which were actually Dec. 28 and Sept. 12 – on Jan. 1 with their school friends.

But Ms. Salim can't bring herself to do that "It's just another day of the year for me. It's New Year's for me, that's all," she said.

As Ms. Salim and Mr. Abdulmunem struggle to get Jan. 1 scrubbed from their IDs, some refugees are pleased with their new birth dates.

A few years ago, Jibril Ibrahim was at home in Edmonton with his kids watching a YouTube video of a Somali comedian. At one point, the comedian joked about how all Somalis are born on Jan. 1 – and his kids lost it.

"They were laughing. They're like – " Mr. Ibrahim pauses, his story interrupted by his own uncontrollable laughter, "'Dad, you were born Jan. 1!' "

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While many in the Somali diaspora were assigned the Jan. 1 date of birth, Mr. Ibrahim, upon arriving in Canada in 1989, was allowed to choose that date because he had grown up only knowing the year of his birth. Overwhelmed by all the things he had to adjust to in his new life, far from Mogadishu, he figured he'd keep it simple.

"Every document you have to fill, you have to fill [the date] in. After a while it became easier for me to remember Jan. 1," he said. "I didn't know the month, I didn't know the day, and you cannot leave it blank, right?"