Is heat out side different than heat in side the house? The reason I ask , is I have notices any thing below 65F / 18C is too cold to wear shorts out side .But in the house any thing below 73F / 23C is bit chilly to wear shorts in the house.
I wonder why the difference.
I also wonder why its 12 degrees warmer in the house. At night time it goes down to 53F / 12C out side!! But in the house it is 73F / 23C to 77F / 25C
Your house may have a draft, or cold surfaces ?
But anyway, your brain can work out what you are doing … if you are likely to be sitting around doing nothing, it decided ‘hey, legs are cold’. While if you are outside in shorts you are liable to be walking if not running…
Night time drops are due to infrared loss into the clear sky.
Your house is an insulator . The ground under the house is a supply of heat if the ground is warmer … So your house gets heat from the ground and doesn’t lose so much to the air/sky…
And devices (water heater, refridgerator, fans, lights, people ) operating in your house make heat. A person is a 1400 Watt heater !
Ah, closer to 100 than to 1400. Here’s a nice little chart. I’m told that the number approximately doubles if you’re doing heavy exercise or hard labor.
But, yes, no doubt about it, put together a nice cocktail party with twenty people in a crowded living room, and they heat the place up noticeably. The human body is capable of generating a surprising amount of energic heat…
(As the line that was excised from a Star Trek episode by the censors would have it, “…depending on the skill of the operator.”)
In addition to getting radiant warmth from sunlight, you’re likely moving around or at least standing when outdoors, which keeps you quite a bit warmer than just sitting in a chair inside. I imagine quite a lot of it is also psychological. You expect the outdoors to have harsher weather than the inside of your safe, comfy house so your brain ignores some of the discomfort outdoors (or accentuates the discomfort indoors).
Also, the temperature outside is given as the shade temperature. In the sun it will be a lot warmer, and if you are outside you may be in the sun some of the time, which will keep you warmer.
I vaguely remember from my night school days that each adult body generates 600 BTU’s of heat.
I remember one time I was on a poor cooling call on a brand new 12000 BTU window shaker in a 24 by 24 foot room. I couldn’t figure out the problem…size was about right.
Asked what the room was used for… “Bridge Club”. Asked how many people…“24”.
Bingo.
I think the other poster is right (the lack of sun light and humidity is why it has to be 73F / 23C to 77F in house to wear t-shirt and shorts. .
And I read on a thread similar to this that any thing below 65F / 18C is too cold to wear t-shirt and shorts out side .
Also I read some people in Floridian develop a intolerance to the cold where any thing under 70F is too cold to wear a t-shirt and shorts out side !! Where some one from New York any thing below 60F is too cold to wear a t-shirt and shorts out side.
Turn the computer and TV on and you can probably heat the room by degree or two.
Since 1 watt = 3.21 BTU/hr - and the heat output values range from ~70 - 150 watts (YMMV, apparently) - you’re both (roughly) right. Yay math! 
That still does not explain why it gets colder at night.
Assuming you’re talking about the question you raised in your original post:
The materials of your house (the roof, the walls, etc.) are heated up during the day, due to the sun, and the warm air temperature. They are slower to lose that heat than the surrounding air is, once the sun goes down, and so, by dawn (usually the coldest part of the night), they’re still likely to be significantly warmer than the temperature of the surrounding outdoor air.
You are much more likely to be active outside. If I try to sit on my outside porch, even at 23 deg, I feel chilly just as if I were inside.
When I spent six weeks in July in Sydney one winter, someone told me that I would feel that the outside temperatures would feel warm (typical high, 15) while inside would feel quote cool (typical high, 15) and so it proved. There was no central heat, although I did have–and use–a space heater.
Is English not your first language? “Outside” and “inside” are each single words, not two-word phrases.
It gets colder at night because heat is provided by the sun, and at night the sun is busy heating up the other side of the world.
You’re also more likely to spend less time outside.
I mean, 32F / 0C isn’t really that cold if you’re just going outside for less than 15-20 minutes.
Stay outside all day in that same temp and you’ll find that it’s colder than it seems.
That’s why the OP finds 73 too chilly for shorts inside, but 65 is too chilly outside- they’re probably spending a lot more time at 73 than at 65 in those situations.