  We investigate, on the basis of CCD Stroemgren photometry, the ages and
metallicities of six LMC clusters together with their surrounding field
population. The clusters and metallicities are: NGC1651 (in the range
[Fe/H]=-0.65 dex to -0.41 dex), NGC1711 (-0.57+/-0.17 dex), NGC 1806
(-0.71+/-0.23 dex), NGC2031 (-0.52+/-0.21 dex) and NGC2136/37 (-0.55+/-0.23
dex) and NGC2257 (-1.63+/-0.21 dex). In the cluster surroundings, we found
about 650 field stars that were suitable to be used for a determination of an
age-metallicity relation (AMR). Our method is to estimate ages for individual
stars on the basis of Stroemgren isochrones with individually measured
metallicities. With this method we are able to sample the AMR of the field
population up to 8 Gyr. Our metallicity data are incompatible with models
predicting many metal-poor stars (G-dwarf problem). The metallicity of the
field population increased by a factor of six, starting around 2 Gyr ago. The
proposed AMR is consistent with the AMR of the LMC cluster system (including
ESO 121 SC03 and three clusters with an age of 4 Gyr).
