Ancient Indian culture was inextricably tied to Hindu religion, observance of dharma, the agrarian way of life and the time of the year. Even if there were days where regular occupations were put on hold, such "holidays" mandated other observations. For e.g., pitR tarpanas on amavasya, upavaasa on ekadasi etc. And then there are some activities that must be performed everyday; for e.g., there is no holiday for sandhya worship.
Hindus regularly had harvest festivals / celebrations. Grains were stored in anticipation of rainy and winter seasons. The rainy season was meant for limiting travel, and scholarly undertakings. This is also called chaturmasya and while sanyasis observe chaturmasya, non-sanyasis worship them and seek tutelage/deekshas during this season.
Winter coincides with kaartika maasa and dhanurmaasa which have their own set of observations such as snaana, upavaasa, etc. Winter ends with the observation of mahaashivaraatri.
A lot of these holiday rituals still continue to this day. Dakshinayana was/is seen as a period for spiritual sadhana and uttarayana is ideal for worldly undertakings.
" How were the weekly/monthly/yearly Holidays in earlier times? "
- Not sure I follow. Astrology and panchaanga are ancient subjects and all kaala maana was done based on these. There are primarily 3 siddhaantas /calendars followed in different parts of the country - brhaspati (mostly north India), chaandramaana (mostly south) and souramaana (I believe this is what is followed in the deep south - tamil nadu etc. their calendar is slightly off from that of AP/karnataka)
"Where there specific Hindu tithy for them? "
Almost all tithis in the Hindu calendar have some specialty attached to them. However, cessation of work is associated with tithis like ekaadasi, amavasya, eclipses etc.
""extra Qn" -- Any specific activity during those days apart from resting & enjoying?"
Answered briefly above. The specific activity depends on the tithi.
Conclusion : No holiday for dharma.
EDIT: Further to your comment on " How were the weekly/monthly/yearly Holidays in earlier times? "
The western world determined their holidays based on their theories of how the world came into being. Christianity chose Sunday as holiday because according to them, God rested from creation on this day (see Sabbath). Summer vacations usually apply to schools and colleges.
In ancient India, veda pathanam started or resumed with upakarma (typically in the month of Shravana). Vedic studies are paused in the month of Pushya (references needed). Note that studies again coincide with dakshinayana and pause coincides with uttarayana. There was no concept of weekend and cessation of activity in Hindu culture. We did have fortnightly breaks in the form of ekadasi; however a different set of activities are prescribed for ekadasi (stated above). [Our uttarayana and dakshinayana nirnaya coincides with Narayana "going to sleep" and "waking up". However, the difference between Hinduism and other religions/cultures is that there are different activities prescribed for each block of time. There is no actual shirking of dharma and holidaying.]