Yesterday 
So, here it is.
It's peak season here in Michigan, where the Mosquito is considered by some to be the Official State Bird.
Image Source
I have no affiliation with these people but feel free to click on the image and buy a shirt from them.
There is a commercial product called Mosquito Barrier produced by people that realized they never noticed mosquitoes around garlic fields.
Image Source
Again, no affiliation with these people but if you want to just buy the stuff, click on the image.
I find it interesting that Garlic has been suggested to repel vampires in folklore.
I'm too cheap to buy it if I can make something relatively effective at a substantial savings.
If you want to dig into the how and why it works, click on the Image Source link above and read through their site.
Without any further song & dance here's my method.
For best results this should be prepared about 12 hours in advance before using.
What You Will Need
Any links included from here on will be affiliate links for my account at Amazon. Following them to Amazon will not cost you any more but Amazon will pay me a commission for any purchases you make and I will use that to buy SP with.
A pump up sprayer, 1-2 gallon is sufficient. 2 Gallon Lawn and Garden Sprayer
Vegetable Oil (1/4 Cup for a 1 Gallon sprayer & 1/2 Cup for a 2 Gallon sprayer)
2 Cups of Chopped Garlic (I buy it by the Quart for cooking)
Dish SOAP not detergent (soaps are made from natural products and detergents are made from man-made or synthetic products).
There is anecdotal evidence that naturally scented soaps like Geranium and Lemon Verbena have some effectiveness repelling mosquitoes.
One Knee High Nylon Stocking. Here's an 8 pack of Knee High Nylons, you can save the rest for when winter comes because I'm going to be writing a post about an off the grid method for preventing and melting ice damns.
I also add 8-10 drops of Citronella Oil
Here's a 3-Pack Variety of Mosquito Repellent Essential Oils - Citronella, Lemongrass & Grapefruit if you really want to go whole hog.
Insert one nylon stocking into the mouth of the sprayer and stretch the open top of the nylon over the rim of the sprayer so you can use it as a funnel.
Add about 2 Cups of Garlic to the nylon stocking, loosely tie a knot in the top of the stocking and drop it into the sprayer.
The nylon stocking allows the Garlic oil to permeate the water you're going to add but prevents bits of Garlic from clogging the nozzle of the sprayer.
Add the vegetable oil (again 1/4 Cup for a 1 Gallon sprayer and 1/2 Cup for a 2 Gallon sprayer.)
Add 2 -4 Tablespoons of the Soap and 8-10 drops of whatever essential oils you decide to use.
Add enough warm tap water (or warm distilled water if you like) to top off the sprayer.
Insert the pump unit into the sprayer and loosely screw it down.
Swirl gently to mix the ingredients (mostly the soap & the oil).
Now simply let the ingredients steep in the sprayer for about 12 hours and you're ready to spray.
Usage
This works best when there hasn't been rain for a day or so and any rain that falls after application severely reduces the effectiveness.
Spray the area you want to repel the mosquitoes from. Spray while moving the wand in a back & forth pattern in front of you. It's not necessary to totally overlap passes over the area you're trying to cover, I've left gaps as big as 2 feet between passes and still gotten good results.
Gently swirl the ingredients inside the sprayer before stating and occasionally while spraying.
I am extremely frugal and will fish the nylon stocking out of the sprayer, untie it, add another cup of fresh Garlic to the 2 Cups already there and re-tie the stocking and make a second batch of spray that I let steep for 24-48 hours.
I feel I should caution you at this point that there is a strong possibility for weight gain using this method.
It makes me crave Garlic Bread and Lasagna.
But it keeps mosquitoes away.
Here's an older post (past it's payout date) about Getting Rid of Wasps & Hornets Without Chemicals