I would prefer going to mukteshwar, Dhanaulti, Chamba, Munsiyari rather than Lansdowne. It is quite crowded now a days and their is nothing much to see apart form one suicide point.
You can go there anytime around the year. But winters are preferred as it is not at very much height and in summers the temperature is high for mountains. This place is best during Monsoon.
You can go there around the year. It totally depends on your choices. September-October is best for beautiful flowers and greenery. November to February is best for cold weather. March to June is pleasant. July to August is bit risky if there is heavy rainfall.
The best time to visit Lansdowne is October – March (In winters) and April – June (In summers). The weather is pleasant during these months.
https://www.tripoto.com/trip/lansdowne
In winter you go. Or August end. Weather becomes very beautiful after monsoon. If you want to see the weather of August end. So please visit my profile.