What Do You Call Someone Who Has the Same Birthday as You?

You’re looking for a word to describe someone with the same birthday as you, but there isn’t a precise term for this in English.

No matter! Over the years, people have come up with many phrases to describe this phenomenon, and we’ve listed them below!

Words for Someone Who Has the Same Birthday as You

  • Birthday twin
  • Astro twin
  • Date twin
  • Birthday buddy
  • Star twin
  • Birthday mate
  • Birthday fellow
  • Cosmic twin
  • Astrology twin
  • Irish twin
  • Birthday companion
  • Birthday bestie


  • A person who was born on the same day as you, but not necessarily during the same year, can be called your “birthday twin.”
  • An “Astro twin” is an example of what to call someone who has the same astrological birth chart as you because you were born at the same time and in close proximity.
  • If someone is born on the same day in the same year as you, but at a different time or place, they are called your “date twin.”

Don’t go anywhere! In the next section, we’ll discuss our three favorite nicknames and astrology terms for a person who has the same birthday as you.

Moreover, we’ll show you some examples using each of these terms!

Birthday Twin

According to the Urban Dictionary, a common expression for someone who has the same birthday as you is a “birthday twin.”

Generally, this phrase simply means that you and the other person were born on the same day in the same month. Therefore, you can still be “birthday twins” if you were born in a different year from one another.

However, if you also happen to have been born in the same year, you get an even more special title! Mono-diurnal birthday twins are born on the same day of the same month in the very same year. It isn’t difficult to see where this term comes from.

After all, Merriam-Webster defines “diurnal” as “of, relating to, or occurring in the daytime.” Moreover, “mono” means “one, alone, or single.”

Therefore, when combined, you get “mono-diurnal,” which has come to mean “occurring on the same day.”

Finally, let’s see a couple of example sentences making use of this phrase:

Person 1: I was born on March 7th.

Person 2: How funny, so was I! I guess that makes us birthday twins.

Graeme and John attributed their similar personalities and interests to the fact that they were mono-diurnal birthday twins.

Astro Twin

When two people are born on the same day at the same time, they will inevitably have what astrology enthusiasts call a similar “astrological birth chart.”

Essentially, an “astrological birth chart” is a snapshot of the sky at the moment of your birth. For believers in astrology, the position of the sun, moon, and various planets creates a unique chart for each person. Moreover, it is said to influence the person they will grow up to be.

Therefore, “Astro twins” will be born on the same day, at the same time, in the same year, and at the same place. If these conditions aren’t met, they won’t have the same birth chart since the sky would be different across different countries.

Thus, meeting your “Astro twin” is a far rarer occurrence than simply meeting your birthday twin. Moreover, you may notice some spooky resemblances between the two of you on account of your near-identical birth charts.

Consider the example sentences below:

Gordon is my Astro twin, and that’s why we’re so close. We like all the same foods, have the same sense of humor, and even walk at a similar speed!

If I ever meet my Astro twin, I fear we won’t get along since I barely like myself.

Date Twin

When you share a birthday with someone, but you were born at a different time and place, you would simply call them your “date twin.”

Date twins are born on the same day of the same month during the same year. However, they don’t carry the same astrological significance as “Astro twins” since they may be born at different times or in different areas.

In other words, their astrological birth charts would not be as similar as “Astro twins.” Therefore, there’s no reason they should be eerily alike in some way.

Thus, if you ever meet your “date twin,” you won’t get a cosmic doppelganger. Nonetheless, you’ll probably still have a lot to talk about!

Finally, let’s see the phrase “date twin” in a few examples:

Carley is my date twin, so we always have a shared birthday party.

It was a lovely dinner, but then he asked me when my birthday is and proceeded to call us date twins. It was a bit odd to say to someone you’re on a date with.