The long stretches of the year in which work is traditionally not begun: Adhik Maas, Chaturmas, Pitru Paksha and the two Kharmas windows. Each one is dated exactly for your city, and each one is shown with the source behind it - or, where the search of the consulted texts came back empty, with that stated plainly instead of hidden.
Dated by the sunrise at New Delhi. Which civil day a lunar boundary falls on is decided by sunrise, so these dates can move by a day with the city - change it above if you are elsewhere.
Every period below carries two separate claims: WHEN it runs, which is arithmetic and astronomy, and WHY it is avoided, which is doctrine. The first can always be computed. The second sometimes has a source and sometimes does not. They are shown apart, and they are never collapsed into a single yes-or-no for a date.
Every period on this page carries two separate statements, and they do not stand or fall together. The first is WHEN it runs. That is calendar arithmetic and astronomy: the Sun's sign at two consecutive new moons, the instant a tithi opens, the moment of a sankranti. It can always be computed, and it needs no scriptural source, only a correct rule.
The second is WHY it is avoided. That is doctrine, and it is the claim that has to trace to a named text. Sometimes it does. Sometimes the search comes back empty and present-day almanac practice is all that is left. This page shows the two apart, so that an exact date can never lend its precision to a prohibition that has no text behind it.
It also does not answer "is my date barred, yes or no". The periods come from different kinds of authority and no source weighs them against one another, so a single verdict would be this site's own weighting dressed up in borrowed authority. The periods are listed with their standings; the weighing is yours.
A lunar month runs from one new moon to the next, about 29.5 days. A solar month runs from one sankranti to the next, about 30.4 days. Because the lunar month is shorter, a lunation occasionally slips entirely between two sankrantis and contains none at all. Sewell and Dikshit state the rule directly: the lunar month in which there is no sankranti is called an adhika, that is, an added or intercalated, month, while a month that does carry a sankranti is nija, the true or regular month.
Under the naming rule in general use, the intercalary month takes the name of the natural month that follows it, so the same name appears twice about a fortnight apart. The second one is then called Nija. That is why an intercalary year has, for instance, both an Adhika Shravana and a Nija Shravana, and why a date given only as "Shravana Shukla Panchami" is genuinely ambiguous in such a year.
The one prohibition on the intercalary month that this app can name at chapter and verse is narrow: the annual shraddha is not performed in it. The wider modern rule, that all auspicious work waits for the Nija month, is shown on the page as the present-day usage it is, separately from the sourced one.
Chaturmas runs from Devashayani Ekadashi, the eleventh tithi of the bright half of Ashadha, to Prabodhini Ekadashi, the same tithi in Kartik. Both boundaries are Ekadashis, and this site already reckons every Ekadashi twice, because the Smarta and the Vaishnava lineages use different rules: the Smarta takes the day whose sunrise falls inside the tithi, while the Vaishnava additionally rejects that day if the tenth tithi has run into the last four fixed ghatikas before sunrise, moving the fast to the next day.
When the two rules pick different days, Chaturmas has two start dates or two end dates, and the page shows both. Neither is corrected into the other. There is also a case in which neither rule selects a day at all: a tithi can open after one sunrise and close before the next, so no civil day carries it. The page says so and gives the exact tithi span instead of guessing a date.
In a year with an intercalary month between the two Ekadashis the span carries five lunar months rather than four. The name does not change; the count of months inside it does. This is the most common reason a printed almanac and a computed calendar appear to disagree about Chaturmas.
Kharmas names the two stretches in which the Sun stands in sidereal Dhanu (Sagittarius) and in sidereal Meena (Pisces). The astronomy is not in question: the ingress instants are computed from the Sun's sidereal longitude to sub-arcsecond precision, and the page prints them to the minute.
What could not be found is a chapter and verse for the prohibition. It appears in every modern almanac and in none of the texts consulted for this project. So the dates ship exactly as computed, in their own tier, under their own heading, with the absence of a source stated on the row rather than left for the reader to assume otherwise.
One further caution about these two: the page gives the ingress and egress INSTANTS. Which civil day a solar month is held to begin on is a separate question, and the four regional rules recorded at Article 28 of the Indian Calendar - Orissa, Tamil, Malabar and Bengal - genuinely disagree about it by as much as two days. The engine computes all four and ranks none, and none of them is applied to the instants shown here.
Pitru Paksha is the dark fortnight of amanta Bhadrapada, closing at Sarva-Pitru Amavasya. The same fortnight is called Ashvina Krishna under the purnimanta reckoning, which is one fortnight with two names rather than two candidates.
The fortnight is enumerated here by the afternoon, not by sunrise: a day belongs to it when the dark half has actually reached its aparahna, which can be a day still called Purnima at sunrise. That is the same anchor the shraddha page uses, and it is why the count of days is not always sixteen.
What the texts prescribe for this fortnight is a rite. The wider modern practice of deferring purchases and new undertakings across the whole of it is shown separately, as usage, because a rule that something must be done then is not the same claim as a rule that nothing else may be.
Holashtak, the eight days before Holi, is named on other pages of this site as a period to avoid. It is not dated here. It would have been easy: it is eight tithis this engine already computes, Phalguna Shukla 8 to Purnima. It is not dated because a search of the consulted texts found nothing carrying the observance, under that name or any other, and dating it would have manufactured a prohibition out of the fact that the arithmetic works.
A Purnima-to-Purnima reckoning of Chaturmas is likewise left uncomputed, for the same reason, and said so on the page: the Ekadashi dates given here are the reckoning this app can source, not a claim that no other reckoning exists.
These refusals render at the same size as the answers. A refusal in small print at the bottom of a page is a disclaimer. A refusal set beside the findings is a result, and for a reader who came looking for Holashtak dates it is the more useful of the two.
The Vivah, Griha Pravesh and other muhurat finders on this site work day by day. They check the tithi, the nakshatra, the weekday, the yoga and the combustion of Jupiter and Venus, and they mark every day accordingly. They hold no month-level rule, so they do not skip Adhik Maas, Chaturmas, Kharmas or Pitru Paksha for you.
That is what this page is for. Pick your date range in a finder, then check it here.
For educational purposes. Astrological interpretations are traditional and not a substitute for professional advice.