A kaala starts at 6 in the morning no matter what time the sun rises. The day is split into 16 kalas, 8 during the day and 8 at night. The kaalas last 1½ hours, which makes exactly 12 hours in each part of the day and night all year round and in every place. The first kaala starts with the day lord and continues around the kalachakra in a clockwise manner. So if the day is Monday, the first kaala is ruled by Moon (6 to 7:30). The next kaala would be of Rahu from 7:30 to 9:00. I have made a chart to simplify this, but it can easily be calculated by remembering the order of the planets on the kalachakra. The best time to do a weekly puja to a planet are on the day of the sign lord at the kaala of the planet. So in your horoscope if you have chandra in mesha, the best time your Chandra Puja is On tuesday at Moon Kaala (1:30-3:00). If Jupiter is in Capricorn then weekly Guru puja/upaya can be done on Saturday at 1:30 to 3:00. The timing can even get more specific if the day and night signs are taken into account. If Venus is in the Mercury’s night sign, Gemini, then the Upaya is best done Wednesday night at 7:30 to 9pm. If Venus was in Virgo, Mercury’s day sign then it would be better to do the puja Wednesday morning at 7:30 to 9am. This can be followed in many cases except when the time is late in the night. For example, Mars in Sagittarius would have its best time on Thursday night at 3 to 4:30am.
Say you have to worship Surya devata on Shasti or Chaturdasi – these are auspicious because they are tithis ruled by its kalachakra opposite likewise worshipping the chandra on Panchami and Trayodashi is auspicious because these tithis are ruled by the chandra’s opposite, Guru.
Guru upaya is most powerful on a thursday, but again if that thursday falls on a dwitiya or a dashami its considered the best, especially when thursday falls on a dashami its called Sudasa vrata, which means the su (good) dasa (time period) begins and the dur (bad) dasa ends.
Worship of budha [mercury] is auspicious on ashtami and amavasya to destroy remove the evil effects of Rahu. When wednesday falls on an ashtami it is called Buddhastami. These days are used when a certain upaya like a single puja is advised to remove the ill effects of a planet.