I'm editing a fic right now, and checking for canon compliancy, and I was wondering if anyone knew Petunia's birthday? Please help ASAP!
Something tells me it wasn't during the summer, because it would have been mentioned during Harry's time with the Dursleys.
Nowhere on the Lexicon is Petunia's birthday mentioned. So, I'd say you have free reign over this topic, although I agree with Something Sinister.
Just an addendum to what was previously said; Lily is younger than Petunia, although it is not explicitly stated how much younger.
The general idea when looking for children on the genealogical record is to go *about* every two years. In theory, and this does not always work in practice, so do not use this as a way to prevent pregnancy, a woman who is exclusively breastfeeding an infant on demand will not ovulate until or after that child starts taking solid foods, typically at about six months. So theoretically, 40 week pregnancy plus 24 weeks of breastfeeding suppressed ovulation plus 40 week pregnancy=104 weeks, and there are 52 weeks in a year.
However, this is not an absolute and I have known women to get pregnant *within six weeks* of delivering their last child, and certain there are women who have more difficulty getting pregnant on that schedule even when they try.
I had the exceptions explained to me a while back, actually. I think that modern women can relatively commonly become pregnant almost imediately after giving birth, and it's got something to do with diet, but I don't remember what it was. Lactose, maybe? Since people drink so much milk these days. I don't remember... And that wouldn't really make sense because my aunt is lactose intolerant and there's a year and two months between my two youngest cousins. But I've known siblings who were born within ten months of each other.
Just thought I'd mention it.
I know a woman who was pregnant seven times in seven years.
And my sister and brother are 11 months apart.
But in general this is not a great idea. For one, pregnancy is *really* hard on a woman's body. Yes, it's natural and yes, it's required for the survival of the species. But there's an immense amount of weight gain and weight loss over a fairly short period of time, there's any number of stretching going on, internally and externally (not just the abdomen, but it's not uncommon for a woman to gain enough weight that she'll get stretch marks on her legs and arms, too) and being the sole provider of blood, nutrients, water, oxygen and waste disposal for another human being requires an IMMENSE amount of energy, calories and nutrients on the part of the mother.
Further, whether she gives birth vaginally or by Caesarean, even assuming no other complications, a woman isn't usually going to be cleared to resume sexual activity by her doctor until 6 weeks have passed. Women who have done so report a great deal of discomfort and there are increased chances of infection if *anything* foreign is introduced (which is why they're also not cleared to use tampons).
Having said all that and back to the original question, I'd make Petunia at least sixteen months older than Lily but no older than three years, I think. Snape ran across them when they (Lily & Snape, who are within 3 weeks of each other in age) were nine or ten, and they were at a playground. Maybe in the late 60s (that first scene happened in 1969 or 1970) it was different, but nowadays, you won't usually catch a fourteen year old at a playground.
You might have good luck browsing traits of various zodiac signs, and picking one that suits her, and placing her birthday in that range.