Grab a classic Kolkata bakery breakfast (eggs, toast and pastries) at Flurys before you leave the city or pick up fresh local snacks at a highway bakery if departing earlier; good fuel and cash-up point.
Stop at a clean highway dhaba for a hot thali or Bengali lunch to refuel you and the car; these stops break up the long drive and offer regionally familiar food.
Have a relaxed dinner at your hotel or a recommended local restaurant; try regional Bengali dishes or simple tandoori/veg options and rest early for the next day.
Arrive Siliguri, check into your hotel and if time permits take a quick visit to local markets (Hong Kong Market or City Centre) to buy snacks for the hill drive and supplies.
Stroll around Mirik’s Sumendu Lake and take a paddle boat to enjoy the calm water, island shrine and surrounding pine-lined hills; the boating counter normally operates from early morning until late afternoon—check local timings on arrival.
Have lunch at Glenary’s (famous bakery & restaurant) or another well-known café on the Mall for sandwiches, continental or pizzas in a colonial setting.
Walk the Mall and Chowrasta area to take in the colonial architecture, shops, local handicrafts and panoramic ridge views; easy orientation for the town.
Visit the Darjeeling Himalayan Railway station; if the toy train joy rides are operating and you have time, take the short heritage ride (schedules vary—confirm in advance).
Depart very early (pre-dawn) for Tiger Hill to watch the sunrise over Kanchenjunga—the classic Darjeeling experience; viewpoint can be crowded so go early. Tiger Hill visits are typically pre-dawn to ~6:30am.
Visit Batasia Loop for the panoramic rail loop and war memorial, then the nearby Ghoom Monastery (Yiga Choeling) to see historic Tibetan Buddhist art; both are easy short visits and open in the morning.
Explore the high-altitude zoo (specializes in snow leopard and red panda) and the adjoining Mountaineering Institute and museum—both usually open from ~9:00/9:30am to mid-afternoon and make a great educational visit.
Take a guided tour of Happy Valley Tea Estate (confirm tour times; typically mid-morning to late afternoon) to learn tea processing and sample fresh brews in the vineyards.
Descend the mountain roads to Siliguri; this drive typically takes 2–3 hours depending on traffic and stops—arrive midday and prepare for the long highway leg south.
Start the lengthy return drive along the highway. Depending on your pace you can aim to reach Kolkata late at night or break the return with an overnight stop mid-route (recommended if tired).
Estimated arrival time back in Kolkata if you drive straight with short stops; alternatively split this leg into two days to arrive refreshed the next morning.