How is the execution period calculated?
Ok, here is a more "human" and less robotic version of the matter:
The famous execution period in a public tender, basically, is the time you have to carry out a contract since you start until you deliver it, with Lacito and everything. And yes, it's key - if you spend, you eat penalties ... or worse, you stay out of the game.
Everything starts when the administration (that is, the one who puts the pasta) takes out the tender. That's when the countdown begins. What does that period depend on? Well, of a lot of things: how big or complicated the project is, the resources you are going to need (people, materials, coffee ... whatever is needed), and brown that may arise along the way, from technical trouble to legal problems. If you see that the thing smells at a potential disaster, better margin, because then the crying comes.
Do not forget: the deadline is not just to put bricks or whatever you have to do. It also tells the time you lose (sorry, "invest") doing paperwork, reports, eternal meetings and all that paraphernalia that nobody tells but is always there.
The deadline can come in days, weeks, months or years, depending on the size of the mess. And be careful, sometimes they put it continuous (without holidays or bridges) and other times they let you breathe a little. Ask well, because then the scares come.
Companies that get into this have to spin fine with the calculation. If you flip and promise to finish before possible, then the hurry, errors and fines arrive. If you are too conservative, you don't want the tender. Therefore, yours is to surround themselves with people who know management and tenders, of those who have already seen everything and do not scare easy.
Ah, important detail: the Public Sector Contract Law is not an ornament. Mark maximum and minimum deadlines that must be respected yes or yes. If you pass them through the lining, they can throw you out of the contest or put a sanction. So not to tempt luck.
Anyway, calculating the execution period well is vital if you do not want trouble. You have to know what the project is about, what can go wrong, and how long you really need. If you don't do it well, you can stay out or, worse, get into a eggplant of delays and penalties. So eye, cold head and calculate with desire.