How to create Gantt charts

You may use TimelinePlot with the PlotStyle option.

For a project with schedule of start date and duration for a few teams.

SeedRandom[23032]
schedule =
 Partition[
  Transpose@{
    RandomSample[
     DateRange[DateObject@{2018, 2, 1}, DateObject@{2018, 2, 28}, "Day"], 12],
    RandomInteger[{2, 7}, 12]
    },
  3]

Then

TimelinePlot[Map[Interval@{First@#, DatePlus @@ #} &, schedule, {2}],
 PlotStyle -> Thickness@[email protected],
 PlotLegends -> SwatchLegend[Automatic, StringTemplate@"Team `1`" /@ Range@4]]

Additional formatting can be added by referring to the documentation.

Hope this helps.

Using the data schedule from @Edmund's answer, (1) wrapping each date range with Labeled and (2) modifying FrameTicks to add additional labels:

ranges = Map[Interval@{First@#, DatePlus @@ #} &, schedule, {2}];
boxlabels = Style[ToUpperCase@#, 12] & /@ RandomWord["Noun", Length[Join @@ schedule]];
labeling = Thread[Join @@ ranges -> boxlabels];
labeledData = Labeled[##, Before]& @@@ # & /@ (Transpose[{#, # /. labeling}] & /@ ranges);
grouplabels = StringTemplate@"GROUP `1`" /@ Range[Length@schedule];
groupsizes = Length /@ ranges;
ticklabels = StringTemplate@"PROJECT `1`" /@ Range[Length[Join @@ schedule]];
spacings = 4;

tlp = TimelinePlot[labeledData, ImageSize -> 700, LabelStyle -> 14, 
    Spacings -> spacings, Frame -> True, 
    PlotMarkers -> {Automatic, 1}, AspectRatio -> 1/GoldenRatio, 
    PlotRangePadding -> {{Scaled[.25], Automatic}, {Scaled[.02], Scaled[.05]}}, 
    PlotLayout -> "Stacked", 
    PlotStyle -> Directive[Thickness[.03], CapForm[None]], 
    PlotLegends -> SwatchLegend[grouplabels],
    GridLines -> {{AbsoluteTime@{2018, 2, 15, 8}}, None}, 
    Method -> {"GridLinesInFront" -> True}] /. Point[__] :> Nothing ;

Show[tlp, Options[tlp[[1]], FrameTicks] /. 
   {None, None} -> {MapIndexed[{ spacings #2[[1]], #} &, ticklabels], 
    MapIndexed[{spacings (Accumulate[groupsizes][[#2[[1]]]] - 
          Floor[groupsizes[[#2[[1]]]]/2]), #} &, grouplabels]}]