Fruit bunches should be harvested with secateurs or a sharp knife so as not to damage the cushions on the branches as well as the harvested fruits. The individual fruit bunches should be graded and the immature and spoilt fruits removed, and then packed into plastic containers or bamboo baskets padded with newspaper or other suitable materials.

Source: http://www.doa.gov.my/main.php?Content=sections&SubSectionID=306&SectionID=5&CurLocation=298&IID=

The fruit is harvested by a person climbing the tree and cutting the mature bunches with a knife or pruning shears. Care must be taken not to injure the point at which the bunch is attached to the tree, because future inflorescences may be borne there. In fact, rather than climbing the tree, it might be better to use ladders because this can minimize damage to dormant flower buds. Four to five harvest rounds are made to clean a tree of its crop. Picking only ripe fruit, as judged by the colour change, greatly improves fruit quality. Generally the fruits in a bunch ripen nearly at the same time, but where ripening is uneven, this greatly complicates the harvest. The fruit should be harvested dry; wet fruit goes mouldy when packed.

The harvest season is short, in certain areas it produce two crops per year (although it is not clear whether individual trees produce more than one crop per year) and the timing varies in different regions, so that in major markets the fruit is available from four months ( Thailand, the Philippines: July-October) to eight months (Peninsular Malaysia: June-February).

Source: http://ecoport.org/ep?Plant=2318&entityType=PLCR**&entityDisplayCategory=full

Lansium in Malaysia generally bear twice a year-in June and July and again in December and January or even until February. In India, the fruits ripen from April to September but in the Philippines the season is short and most of the fruits are off the market in less than one month. The fruit can be harvested about 6 months after flower anthesis.