  Star formation histories (SFHs) are integral to our understanding of galaxy
evolution. We can study recent SFHs by comparing the star formation rate (SFR)
calculated using different tracers, as each probes a different timescale. We
aim to calibrate a proxy for the present-day rate of change in SFR, dSFR/dt,
which does not require full spectral energy distribution (SED) modeling and
depends on as few observables as possible, to guarantee its broad
applicability. To achieve this, we create a set of models in CIGALE and define
an SFR change diagnostic as the ratio of the SFR averaged over the past 5 and
200 Myr, <SFR5>/<SFR200>, probed by the H$\alpha$-FUV colour. We apply
<SFR5>/<SFR200> to the nearby spiral NGC 628 and find that its star formation
activity has overall been declining in the recent past, with the spiral arms,
however, maintaining a higher level of activity. The impact of the spiral arm
structure is observed to be stronger on <SFR5>/<SFR200> than on the star
formation efficiency (SFE$_\text{H$_2$}$). In addition, increasing disk
pressure tends to increase recent star formation, and consequently
<SFR5>/<SFR200>. We conclude that <SFR5>/<SFR200> is sensitive to the molecular
gas content, spiral arm structure, and disk pressure. The <SFR5>/<SFR200>
indicator is general and can be used to reconstruct the recent SFH of any
star-forming galaxy for which H$\alpha$, FUV, and either mid- or far-IR
photometry is available, without the need of detailed modeling.
