  Most planetary discoveries with the K2 and TESS missions are restricted to
short periods because of the limited duration of observation. However, the
re-observation of sky area allows for the detection of longer period planets.
We describe new transits detected in six candidate planetary systems which were
observed by multiple K2 mission campaigns. One of these systems is a
multiplanet system with four candidate planets; we present new period
constraints for two planets in this system. In the other five systems, only one
transit is observed in each campaign, and we derive period constraints from
this new data. The period distributions are highly multimodal resulting from
missed potential transits in the gap between observations. Each peak in the
distribution corresponds to transits at an integer harmonic of the two observed
transits. We further detail a generalized procedure to constrain the period for
planets with multiple observations with intervening gaps. Because long period
photometrically discovered planets are rare, these systems are interesting
targets for follow-up observations and confirmation. Specifically, all six
systems are bright enough (V = 10.4-12.7) to be amenable to radial velocity
follow-up. This work serves as a template for period constraints in a host of
similar yet-to-be-discovered planets in long baseline, temporally gapped
observations conducted by the TESS mission.
