Our pets are our family members, but with few exceptions, two things about them will always remain a mystery. The first is the life that they had before we adopted them, especially if they were a stray rescue from a shelter.

Who was their previous family and what were they like? Or did they even have one? What name did they used to have, and how did they wind up with you?

The other, of course, is when, exactly, they were born. The only exceptions to this are if you adopt from a reputable breeder or rescue a puppy born in a shelter so that the exact date of birth is known. Otherwise, it’s guesswork based on the best estimates of veterinarians, vet techs, or shelter staff.

Guessing your pet's age

Now, there are ways to make a rough estimate of a dog’s or cat’s age based on things like teeth, bone growth, bodily proportions, and so on. Other than the years, you can figure out the same things about humans but only over broader spans of time.

Of course, one thing that very obviously marks humans as adolescents may be non-existent in the case of dogs or cats that were already spayed or neutered by the time they got to the shelter, so never make it to that stage of life.

Generally, estimates will fall into ranges like number of weeks based on puppy or kitten development — which tend to be fairly accurate — and then longer ranges in terms of months and then years as the animal gets older. These are less accurate.

Dogs and cats generally reach full maturity between 12 and 18 months, although larger breeds of both species can continue growing — up to three years old for dogs, and four or five for cats.

Once they reach about seven, they’re just senior citizens, although at least by that point there was probably a human in their life pre-shelter long enough to give a general idea of age.

But let’s say that it’s May and you adopt a dog from a shelter. They tell you that she’s about eleven months old. When and how do you celebrate their birthday?

Choosing which day to celebrate

Different people have different methods of deciding when to celebrate their furry friend's birthday, of course. Some will just celebrate their pet's adoption day. Others will choose the date their previous pet passed in order to make it a double commemoration.

Some people will pick their own birthdays, following the logic that it’s a date they’ll never forget. Others may pick a fixed holiday near their dog’s birth, with Valentine’s Day and St. Patrick’s Day being popular choices.

A more common method is to calculate the approximate month of birth using estimated age. Some people have used the average of the shelter’s estimate and their vet’s estimate as well. From there, the choice of date is wide open.

A lot of people will just make it the first of the month so, for example if they adopted a nine-month-old dog on May 11, then they can either subtract 9 months from May, or just use the easier method of adding 3 months, making the birth month August. Again, the choice of actual day is up to you, the pet parent, and can be whatever you want, although if there’s a day in that month significant to you, feel free to choose that one.

I had one friend who, over the years, always made her dogs’ birthdays January 1st. It was easy to remember, it was already a holiday, and it gave her an excuse to invite all of her friends over, asking them to bring their dogs to join the celebration.

When my family adopted what eventually became my first dog, she was a twelve-week-old puppy. We brought her home around Thanksgiving, so it was very easy to count backwards, putting her approximate birthday near the end of August. I picked August 23, since I had read somewhere that this date was associated with Sirius, the Dog Star.

Later on, after my first dog had passed and I adopted my second, the math also put her birthday in August, so she got the 23rd as well. Dog number three wound up having been born around mid-November, so she got November 14 completely at random.

Of course, keep in mind that it doesn’t matter what date you pick because your dog doesn’t know or care. Sure, they will have some awareness of their own aging as things start to feel different or their senses weaken, but they will obviously not have any awareness of what age they are or when they’re another year older.

Your dog’s birthday is for you, but that’s okay. It gives you an occasion and a reason to celebrate and spoil them at least once a year, and it also helps you keep track of your dog’s age, which is an important number to you and your vet.

Celebrating a cat or dog birthday

So how do you celebrate your dog’s birthday? Almost as many ways as you can celebrate a human’s! Does your dog have a favorite activity, like hiking, playing flying disc at the dog park, or swimming? Then treat them to a day of doing that.

You can also get dogs and cats new toys and, in the case of your dog, there are a lot of pet stores that will let you take them in with you so you can let them pick out their own gift. I remember the first time I did this with one of my dogs.

When I took her to the display bins with all the different bones and told her to take one, the mixed look of disbelief and joy she gave me was a delight to behold. She proceeded to sniff around and then, of course, picked a bone that was almost too big for her to lift. Of course, your pooch might also appreciate a brand new comfy dog bed.

Another approach to gifting is to give your dog a present and let them unwrap it, although be careful with this one. I taught one of my dogs to unwrap her birthday gift, which was very cute at the time but then a disaster the following Christmas, for obvious reasons. It’s also not a good idea to teach your cat this trick.

Fortunately, I was able to untrain my dog at unwrapping people presents by only wrapping hers very loosely in newspaper from then on. This gave them a very different smell and taste than wrapping paper and also took very little effort to open, so it actually did solve the problem.

It’s PAWty time!

Of course, you’re probably going to want to have some sort of celebration in honor of the event, and these can range from a private family get-together all the way up to full-on dog park blow-out with invited guests of the human and canine kind. Yet again, cats kind of get the short end of the stick, but they’d probably prefer the smaller gathering anyway, since that would be all about them.

When planning a dog birthday party, the most important thing to consider is your dog’s personality. Some dogs do great around crowds, dogs, and excitement. Others don’t, so plan accordingly. The same goes for any human guests — it’s probably not a good idea to invite your aunt who is terribly afraid of dogs, for example. Just like any other complex event, it does require advance preparation.

There’s also the food to consider. Everything needs to be dog safe. This means no chocolate, raisins, grapes, and ice cream, among other things. And, besides cake, what else is happening at the pet party? Would you like to have hats, party favors, and a theme?

I developed a nice birthday routine that I’ve used with all of my dogs. On the big day, each of us would get either an appropriately sized steak or cheeseburger, depending on how much money I was making at the time. They’d be the same except that there’d be no condiments on the dog’s burger. Also, I’d cut their food into small, bite-size pieces first so that they wouldn’t try to inhale the thing in one bite.

Instead of a dog birthday cake, I would usually get a muffin in some dog-friendly form. Carrot cake was always a popular choice. And yes, I would splurge for one of those number-shaped birthday candles (up until 9) to put on top, although I’d have to be the one to blow it out, because none of my dogs ever figured that part out.

Of course, they probably also never figured out, “Why is my treat on fire?”

What’s important is to avoid things that contain poppy seeds, or a lot of dairy — think cheesecake. And while muffins lower in sugar are better, sugar-free is not, as these muffins may contain xylitol, an artificial sweetener that can be quickly fatal to pets.

Also, on your pet’s special day, be sure to show them extra attention and affection.

364 other reasons to celebrate

Whether or not you celebrate your pet’s birthday, do remember to celebrate their life and their love every single day. Gifts, fun adventures, and attention aren’t just for that one day out of the year. They’re for every day and every wonderful moment you’ll have together until your pet runs out of birthdays.

But by all means, if you want to take those extra steps on the big day, do so, and don’t feel one bit of guilt about it. Your dog or cat won’t know why it’s happening — but they’ll still enjoy it all the same. And so will you.