The heat cycle of a bitch
The so-called standing days or also called standing heat, describes during the heat of your bitch the toleration phase. The toleration phase is the phase of the rut in female mammals. In this phase the bitch tolerates the mating by a male. You can recognize the standing days by the fact that your bitch stands as soon as a male approaches. Furthermore, her legs are firmly planted on the ground so that the male can easily mount for mating.
Other characteristics of standing heat are that your bitch will arch her back and lay her tail to the side. Bitches are on the lookout for potential males during this phase. This is further enhanced by the bitches spraying certain pheromones to signal that they are ready to mate. The smell, which is sprayed by the pheromones, attracts males. This is also the time when ovulation occurs. Be careful if you do not want to mate your bitch. If you encounter an unleashed male, leave your bitch and wait for the owner to arrive.
The fertile phase of your bitch
The maturation of the eggs that make her capable of fertilization occurs differently in a bitch than in many other female mammals. The maturation of the eggs takes place only after the ovulation, after about 48 to 72 hours in the fallopian tubes, because then the progesterone level has risen sufficiently. However, since exceptions tend to prove the rule, observations have been made in which still immature oocytes were also fertilised. After the maturation of the fallopian tubes has taken place, the eggs are capable of being fertilised for about two days. Ovulation then occurs within 12 to 36 hours.
As a rule, the survival time of the sperm in the genital tract of the bitch is several days. The survival time can even be up to 11 days.

The determination of the mating time
Your bitch's readiness to mate usually starts at the same time as the beginning of the fertile phase. Your veterinarian can determine the best time for mating, which usually occurs once or twice. There will be an examination of hormone levels, which will enable the vet to determine the most favourable days for mating. You can tell if your bitch is in the middle of standing heat by various reactions your bitch has. If your bitch moves the rod set to the side as well as upwards and she pushes it back to a slight hollow back after you have touched it next to the vulva, your bitch is in the standing heat. Your bitch creates by these reactions the best conditions for a successful mating act. At this time of the standing days, however, the vulva must also be swollen to the maximum.

You can also count the days of your bitch's cycle. If you start counting on the first day of bleeding, you can calculate the best days for mating. If your bitch has a light to white coat, you can clearly recognize the beginning of the heat by the first blood. If your bitch has a darker coat, the beginning of heat can be overlooked.
The beginning of the so-called standing days can be easily seen by the swelling of the vulva.
Briefly summarized
Standing days: also known as the standing heat or acquiescence phase
Beginning: The toleration phase begins with the end of bleeding
Signs of the bitch: Firm stand, by pressed back, tail goes to the side as well as upwards