Which lunar days are good for sign a contract?

The tradition favours lunar days 2, 3, 7, 10, 11, 13, 14, 15, 18, 20, 21, 24, 25, 28.

No. The timings are computed from an ephemeris and are exact; the guidance is inherited tradition, whose own authorities disagree on every lunar day. MoonIQ labels which is which.

MoonIQ

Sign a contract, by the Moon

Of 29 lunar days, the tradition favours 14 for this and discourages 13. The lunar day turns at moonrise, so a calendar date usually spans two of them — which is why a date can be good for part of the day and not the rest.

Favourable lunar days for sign a contract

Lunar day 2: This day is named outright as a good one for new contracts in the tradition.
Lunar day 3: The tradition holds this to be a strong day for business decisions, which covers committing to an agreement.
Lunar day 7: The tradition says words spoken today carry special power and favours coming to agreement with bosses, investors and partners.
Lunar day 10: With negotiations, sales and financial transactions all favoured, the tradition treats this as a good day for concluding business arrangements.
Lunar day 11: The tradition encourages making agreements with partners today, though it asks that trade deals specifically be held back.
Lunar day 13: The tradition counts this a good day for hiring, acquisitions and financial matters, which covers formalising an agreement.
Lunar day 14: The tradition allows business commitments today but insists documents and details be checked over again before you decide.
Lunar day 15: The tradition says the outcome depends on your earlier groundwork: sign boldly if it was well prepared, otherwise wait.
Lunar day 18: The tradition describes this as an unremarkable day given to routine and research, with no particular pull either way for agreements.
Lunar day 20: The tradition ranks this among the best business days, good for new projects, sales and financial matters.
Lunar day 21: The tradition holds that transactions run smoothly and new proposals are worth accepting today.
Lunar day 24: Contracting is named outright among the activities the tradition favours on this day.
Lunar day 25: The tradition favours buying, selling and financial transactions today, which covers settling a business agreement.
Lunar day 28: The tradition counts this a favourable day for business dealings, purchases and negotiations coming to conclusion.

Lunar days to avoid

Lunar day 1: The tradition treats this day as one for planning rather than committing, advising that decisions be put off — which would include putting your name to a contract.
Lunar day 4: The tradition favours paperwork and checking over commitment on this day, warning against important decisions such as signing.
Lunar day 5: Apart from settling debts, the tradition advises holding back from financial dealings today, which loosely covers signing a financial agreement.
Lunar day 6: The tradition singles out major property deals for postponement on this day, so large contracts of that kind are discouraged.
Lunar day 9: The tradition warns off deals entirely on this day, saying they may turn out other than they appear.
Lunar day 12: The tradition favours negotiating and compromise today but advises postponing weighty business and commerce, so formal signing is discouraged.
Lunar day 17: The tradition favours sales and presentations today but cautions against concluding deals involving large sums.
Lunar day 19: The tradition advises against taking on anything new or agreeing to proposals on the spot today.
Lunar day 22: The tradition steers this day toward routine and study, warning against commercial dealings and important decisions.
Lunar day 23: The tradition calls this a contentious day and advises against important decisions and negotiations.
Lunar day 26: The tradition warns that offers made today may hide information or ill intent, making it a poor day to commit.
Lunar day 27: The tradition favours completing what is already begun and advises against taking on anything new, such as a fresh agreement.
Lunar day 29: The tradition treats this as a day of rest and asks that transactions and dealings be put off.

What this is, and is not

Inherited material, quoted as received. Checked against the tradition's own named authorities, these readings contradict each other on all 29 lunar days — so treat the guidance as a custom worth knowing, not a finding. The astronomy underneath it is exact: MoonIQ computes which lunar day you are in, and the minute it turns, for your own location.