We should select an appropriate tidhi, nakshatram, yogam for our work. Varjyam, Rahu kaalam, Durmuhurtam are main time periods consider as bad time during a given day. We can get benefits by selecting right time to start a new event or by avoding bad time to start our events.
Each tithi, nakshatram, yogam & karnam have their own merits and demerits. Panchangam tells us which day is good, which day is bad, which time is suitable to start a work etc. Panchangam describes Tidhi, Vaaram, Nakshatram, Yogam & Karnam.