1 This helps keep your upper back straight while having a slight arch in your lower back. 2  Slowly lift by straightening your hips and knees (not your back). Keep your back straight, and don't twist as you lift.  Hold the load as close to your body as possible, at the level of your belly button.
Definition of birthday. 1  1a : the day of a person's birthb : a day of origin. 2  2 : an anniversary of a birth her 21st birthday.
When is your birthday is correct; everyone who has ever had a birthday party knows what a birthday is. But as Quora User points out, it's okay to ask what is your birth date (or birth month or birth year). The structure seems the same, but you are asking for a particular value for the date.