Towards a multi-tracer timeline of star formation in the LMC -- I.\
  Deriving the lifetimes of H\,{\sc i} clouds
  The time-scales associated with the various stages of the star formation
process remain poorly constrained. This includes the earliest phases of star
formation, during which molecular clouds condense out of the atomic
interstellar medium. We present the first in a series of papers with the
ultimate goal of compiling the first multi-tracer timeline of star formation,
through a comprehensive set of evolutionary phases from atomic gas clouds to
unembedded young stellar populations. In this paper, we present an empirical
determination of the lifetime of atomic clouds using the Uncertainty Principle
for Star Formation formalism, based on the de-correlation of H$\alpha$ and
H\,{\sc i} emission as a function of spatial scale. We find an atomic gas cloud
lifetime of 48$\substack{+13\\-8}$\,Myr. This timescale is consistent with the
predicted average atomic cloud lifetime in the LMC (based on galactic dynamics)
that is dominated by the gravitational collapse of the mid-plane ISM. We also
determine the overlap time-scale for which both H\,{\sc i} and H$\alpha$
emission are present to be very short ($t_{over}<1.7$\,Myr), consistent with
zero, indicating that there is a near-to-complete phase change of the gas to a
molecular form in an intermediary stage between H\,{\sc i} clouds and H\,{\sc
ii} regions. We utilise the time-scales derived in this work to place
empirically determined limits on the time-scale of molecular cloud formation.
By performing the same analysis with and without the 30 Doradus region
included, we find that the most extreme star forming environment in the LMC has
little effect on the measured average atomic gas cloud lifetime. By measuring
the lifetime of the atomic gas clouds, we place strong constraints on the
physics that drives the formation of molecular clouds and establish a solid
foundation for the development of a multi-tracer timeline of star formation in
the LMC.
