diff --git a/src/basemisc.jl b/src/basemisc.jl
index 595199e9..18fa2029 100644
--- a/src/basemisc.jl
+++ b/src/basemisc.jl
@@ -37,12 +37,10 @@ macro _mapbase(sig::Expr, imp::Expr)
     doc = "   $sig"
     fdef = Expr(:function, sig, fbody)
 
-    return esc(
-        quote
-            $doc
-            $fdef
-        end,
-    )
+    return esc(quote
+        $doc
+        $fdef
+    end)
 end
 
 # Cumulative functions
diff --git a/src/broadcast.jl b/src/broadcast.jl
index 0a7bd59e..7b597210 100644
--- a/src/broadcast.jl
+++ b/src/broadcast.jl
@@ -13,7 +13,7 @@ Base.broadcastable(x::AbstractTimeSeries) = x
 
 Base.Broadcast.instantiate(bc::Broadcasted{<:TimeArrayStyle}) =
 # skip the default axes checking
-    Broadcast.flatten(bc)
+Broadcast.flatten(bc)
 
 function Base.copy(bc′::Broadcasted{<:TimeArrayStyle})
     tas = find_ta(bc′)
diff --git a/src/combine.jl b/src/combine.jl
index beec8692..04a6711e 100644
--- a/src/combine.jl
+++ b/src/combine.jl
@@ -206,9 +206,11 @@ collapse(ta, month, last)
 collapse(ta, month, last, mean)
 ```
 """
-collapse(
+function collapse(
     ta::TimeArray, period::Period, timestamp::Function, value::Function=timestamp; kw...
-) = collapse(ta, x -> floor(x, period), timestamp, value; kw...)
+)
+    collapse(ta, x -> floor(x, period), timestamp, value; kw...)
+end
 
 # vcat ######################
 
diff --git a/src/modify.jl b/src/modify.jl
index 6088adcb..3d0585f4 100644
--- a/src/modify.jl
+++ b/src/modify.jl
@@ -49,12 +49,15 @@ for f in [:rename, :rename!]
     @eval begin
         $f(ta::TimeArray, colnames::Symbol) = $f(ta, [colnames])
         $f(ta::TimeArray) = throw(MethodError($f, (ta,)))
-        $f(ta::TimeArray, pairs::Pair{Symbol,Symbol}...) =
-            $f(ta, _mapcol(colnames(ta), pairs))
-        $f(f::Base.Callable, ta::TimeArray, colnametyp::Type{Symbol}=Symbol) =
-            $f(ta, map(f, colnames(ta)))
-        $f(f::Base.Callable, ta::TimeArray, colnametyp::Type{String}) =
-            $f(Symbol ∘ f ∘ string, ta)
+        $f(ta::TimeArray, pairs::Pair{Symbol,Symbol}...) = $f(
+            ta, _mapcol(colnames(ta), pairs)
+        )
+        $f(f::Base.Callable, ta::TimeArray, colnametyp::Type{Symbol}=Symbol) = $f(
+            ta, map(f, colnames(ta))
+        )
+        $f(f::Base.Callable, ta::TimeArray, colnametyp::Type{String}) = $f(
+            Symbol ∘ f ∘ string, ta
+        )
     end
 end
 
diff --git a/src/retime.jl b/src/retime.jl
index 1d0a972f..8df412fd 100644
--- a/src/retime.jl
+++ b/src/retime.jl
@@ -46,7 +46,7 @@ _toAggregationMethod(::Val{:sum}) = Sum()
 _toAggregationMethod(::Val{:median}) = Median()
 _toAggregationMethod(::Val{:first}) = First()
 _toAggregationMethod(::Val{:last}) = Last()
-_toAggregationMethof(f::Function) = AggregationFunction(f)
+_toAggregationMethod(f::Function) = AggregationFunction(f)
 _toAggregationMethod(x::AggregationMethod) = x
 
 _toExtrapolationMethod(x::Symbol) = _toExtrapolationMethod(Val(x))
diff --git a/src/split.jl b/src/split.jl
index a8d3eb17..23ad8712 100644
--- a/src/split.jl
+++ b/src/split.jl
@@ -81,8 +81,9 @@ Split `data` by `period` function, returns a vector of `TimeSeries.TimeArray`.
 - `data::TimeSeries.TimeArray`: Data to split
 - `period::Function`: Function, e.g. `Dates.day` that is used to split the `data`.
 """
-Base.split(data::TimeSeries.TimeArray, period::Function) =
+function Base.split(data::TimeSeries.TimeArray, period::Function)
     Iterators.map(i -> data[i], _split(TimeSeries.timestamp(data), period))
+end
 
 function _split(ts::AbstractVector{D}, period::Function) where {D<:TimeType}
     m = length(ts)
diff --git a/src/timearray.jl b/src/timearray.jl
index 351b44ca..2e1e6dc6 100644
--- a/src/timearray.jl
+++ b/src/timearray.jl
@@ -237,8 +237,8 @@ end
         io::IO,
         ::MIME"text/plain",
         ta::TimeArray;
-        allrows=!get(io, :limit, false),
-        allcols=!get(io, :limit, false),
+        allrows=(!get(io, :limit, false)),
+        allcols=(!get(io, :limit, false)),
     )
         nrow = size(values(ta), 1)
         ncol = size(values(ta), 2)
@@ -278,8 +278,8 @@ else
         io::IO,
         ::MIME"text/plain",
         ta::TimeArray;
-        allrows=!get(io, :limit, false),
-        allcols=!get(io, :limit, false),
+        allrows=(!get(io, :limit, false)),
+        allcols=(!get(io, :limit, false)),
     )
         nrow = size(values(ta), 1)
         ncol = size(values(ta), 2)
@@ -301,8 +301,8 @@ else
             row_label_column_alignment=:r,
             column_label_alignment=:l,
             continuation_row_alignment=:c,
-            fit_table_in_display_horizontally=!allcols, # replaced crop keyword for v3 of PrettyTables
-            fit_table_in_display_vertically=!allrows,   # replaced crop keyword for v3 of PrettyTables
+            fit_table_in_display_horizontally=(!allcols), # replaced crop keyword for v3 of PrettyTables
+            fit_table_in_display_vertically=(!allrows),   # replaced crop keyword for v3 of PrettyTables
             vertical_crop_mode=:middle,
         )
     end
@@ -318,27 +318,34 @@ getindex(ta::TimeArray) = throw(BoundsError(typeof(ta), []))
 # single row
 @propagate_inbounds getindex(ta::TimeArray, n::Integer) =
 # avoid conversion to column vector
-    TimeArray(timestamp(ta)[n], values(ta)[n:n, :], colnames(ta), meta(ta))
+TimeArray(
+    timestamp(ta)[n], values(ta)[n:n, :], colnames(ta), meta(ta)
+)
 
 # single row 1d
-@propagate_inbounds getindex(ta::TimeArray{T,1}, n::Integer) where {T} =
-    TimeArray(timestamp(ta)[n], values(ta)[[n]], colnames(ta), meta(ta))
+@propagate_inbounds getindex(ta::TimeArray{T,1}, n::Integer) where {T} = TimeArray(
+    timestamp(ta)[n], values(ta)[[n]], colnames(ta), meta(ta)
+)
 
 # range of rows
-@propagate_inbounds getindex(ta::TimeArray, r::UnitRange{<:Integer}) =
-    TimeArray(timestamp(ta)[r], values(ta)[r, :], colnames(ta), meta(ta))
+@propagate_inbounds getindex(ta::TimeArray, r::UnitRange{<:Integer}) = TimeArray(
+    timestamp(ta)[r], values(ta)[r, :], colnames(ta), meta(ta)
+)
 
 # range of 1d rows
-@propagate_inbounds getindex(ta::TimeArray{T,1}, r::UnitRange{<:Integer}) where {T} =
-    TimeArray(timestamp(ta)[r], values(ta)[r], colnames(ta), meta(ta))
+@propagate_inbounds getindex(ta::TimeArray{T,1}, r::UnitRange{<:Integer}) where {T} = TimeArray(
+    timestamp(ta)[r], values(ta)[r], colnames(ta), meta(ta)
+)
 
 # array of rows
-@propagate_inbounds getindex(ta::TimeArray, a::AbstractVector{<:Integer}) =
-    TimeArray(timestamp(ta)[a], values(ta)[a, :], colnames(ta), meta(ta))
+@propagate_inbounds getindex(ta::TimeArray, a::AbstractVector{<:Integer}) = TimeArray(
+    timestamp(ta)[a], values(ta)[a, :], colnames(ta), meta(ta)
+)
 
 # array of 1d rows
-@propagate_inbounds getindex(ta::TimeArray{T,1}, a::AbstractVector{<:Integer}) where {T} =
-    TimeArray(timestamp(ta)[a], values(ta)[a], colnames(ta), meta(ta))
+@propagate_inbounds getindex(ta::TimeArray{T,1}, a::AbstractVector{<:Integer}) where {T} = TimeArray(
+    timestamp(ta)[a], values(ta)[a], colnames(ta), meta(ta)
+)
 
 # single column by name
 @propagate_inbounds function getindex(ta::TimeArray, s::Symbol)
@@ -348,15 +355,12 @@ end
 
 # array of columns by name
 @propagate_inbounds getindex(ta::TimeArray, ss::Symbol...) = getindex(ta, collect(ss))
-@propagate_inbounds getindex(ta::TimeArray, ss::Vector{Symbol}) =
-    TimeArray(ta; values=values(ta)[:, map(s -> findcol(ta, s), ss)], colnames=ss)
+@propagate_inbounds getindex(ta::TimeArray, ss::Vector{Symbol}) = TimeArray(
+    ta; values=values(ta)[:, map(s -> findcol(ta, s), ss)], colnames=ss
+)
 
 # ta[rows, cols]
-@propagate_inbounds getindex(
-    ta::TimeArray,
-    rows::Union{AbstractVector{<:Integer},Colon},
-    cols::AbstractVector{Symbol},
-) = TimeArray(
+@propagate_inbounds getindex(ta::TimeArray, rows::Union{AbstractVector{<:Integer},Colon}, cols::AbstractVector{Symbol}) = TimeArray(
     ta;
     timestamp=timestamp(ta)[rows],
     values=values(ta)[rows, map(s -> findcol(ta, s), cols)],
@@ -371,8 +375,9 @@ end
 @propagate_inbounds getindex(ta::TimeArray, rows, col::Symbol) = getindex(ta, rows, [col])
 
 # ta[n, col]
-@propagate_inbounds getindex(ta::TimeArray, n::Integer, col::Symbol) =
-    getindex(ta, [n], [col])
+@propagate_inbounds getindex(ta::TimeArray, n::Integer, col::Symbol) = getindex(
+    ta, [n], [col]
+)
 
 # single date
 @propagate_inbounds function getindex(ta::TimeArray{T,N,D}, d::D) where {T,N,D}
@@ -388,8 +393,9 @@ end
 end
 
 # StepRange{Date,...}
-@propagate_inbounds getindex(ta::TimeArray{T,N,D}, r::StepRange{D}) where {T,N,D} =
-    ta[collect(r)]
+@propagate_inbounds getindex(ta::TimeArray{T,N,D}, r::StepRange{D}) where {T,N,D} = ta[collect(
+    r
+)]
 
 @propagate_inbounds getindex(ta::TimeArray, k::TimeArray{Bool,1}) = ta[findwhen(k)]
 
diff --git a/test/retime.jl b/test/retime.jl
index 1914a120..6fc2097c 100644
--- a/test/retime.jl
+++ b/test/retime.jl
@@ -24,6 +24,12 @@ using Statistics
         @test TimeSeries._toAggregationMethod(:first) == TimeSeries.First()
         @test TimeSeries._toAggregationMethod(:last) == TimeSeries.Last()
 
+        # Test function conversion to AggregationFunction
+        custom_func = x -> sum(x) / length(x)
+        agg_method = TimeSeries._toAggregationMethod(custom_func)
+        @test agg_method isa TimeSeries.AggregationFunction
+        @test agg_method.func === custom_func
+
         @test_throws MethodError TimeSeries._toAggregationMethod(:foo)
     end
 
@@ -34,6 +40,10 @@ using Statistics
         @test TimeSeries._toExtrapolationMethod(:missing) == TimeSeries.MissingExtrapolate()
         @test TimeSeries._toExtrapolationMethod(:nan) == TimeSeries.NaNExtrapolate()
 
+        # Test custom FillConstant values
+        @test TimeSeries.FillConstant(42.0).value == 42.0
+        @test TimeSeries.FillConstant(-1).value == -1
+
         @test_throws MethodError TimeSeries._toExtrapolationMethod(:foo)
     end
 
@@ -112,6 +122,11 @@ using Statistics
         @test timestamp(cl_new) == new_timestamps
         @test values(cl_new[:Close][1])[1] == 0.0
 
+        # Test custom fill value
+        cl_new = retime(cl, new_timestamps; extrapolate=TimeSeries.FillConstant(99.9))
+        @test timestamp(cl_new) == new_timestamps
+        @test values(cl_new[:Close][1])[1] == 99.9
+
         cl_new = retime(cl, new_timestamps; extrapolate=TimeSeries.NearestExtrapolate())
         @test timestamp(cl_new) == new_timestamps
         @test values(cl_new[:Close][1])[1] == values(cl[:Close][1])[1]
@@ -277,4 +292,70 @@ using Statistics
 
         ta_new = retime(ta, Hour(1); upsample=:linear)
     end
+
+    @testset "AggregationFunction with custom function" begin
+        new_timestamps = collect(Dates.Date(2000):Dates.Week(1):Dates.Date(2001))
+
+        # Test with custom function: weighted average favouring first value
+        custom_agg = x -> 0.7 * first(x) + 0.3 * last(x)
+        cl_new = retime(cl, new_timestamps; downsample=custom_agg)
+
+        @test timestamp(cl_new) == new_timestamps
+
+        # Verify custom function is applied
+        idx = new_timestamps[2] .<= timestamp(cl) .< new_timestamps[3]
+        cl_values = values(cl[:Close][idx])
+        expected = 0.7 * first(cl_values) + 0.3 * last(cl_values)
+        @test expected == values(cl_new[:Close][2])[1]
+
+        # Test with standard deviation function
+        cl_new_std = retime(cl, new_timestamps; downsample=std)
+        @test timestamp(cl_new_std) == new_timestamps
+
+        # Test with custom function on multi-column
+        ohlc_new = retime(ohlc, new_timestamps; downsample=x -> median(x))
+        @test timestamp(ohlc_new) == new_timestamps
+    end
+
+    @testset "Count aggregation" begin
+        new_timestamps = collect(Dates.Date(2000):Dates.Week(1):Dates.Date(2001))
+
+        cl_new = retime(cl, new_timestamps; downsample=TimeSeries.Count())
+        @test timestamp(cl_new) == new_timestamps
+
+        # Verify count is correct
+        idx = new_timestamps[2] .<= timestamp(cl) .< new_timestamps[3]
+        expected_count = count(!ismissing, values(cl[:Close][idx]))
+        @test expected_count == values(cl_new[:Close][2])[1]
+
+        # Test count with symbol
+        cl_new_sym = retime(cl, new_timestamps; downsample=:count)
+        @test values(cl_new) == values(cl_new_sym)
+    end
+
+    @testset "First and Last aggregation" begin
+        new_timestamps = collect(Dates.Date(2000):Dates.Week(1):Dates.Date(2001))
+
+        cl_first = retime(cl, new_timestamps; downsample=TimeSeries.First())
+        cl_last = retime(cl, new_timestamps; downsample=TimeSeries.Last())
+
+        @test timestamp(cl_first) == new_timestamps
+        @test timestamp(cl_last) == new_timestamps
+
+        # Verify first and last are correct
+        idx = new_timestamps[2] .<= timestamp(cl) .< new_timestamps[3]
+        @test first(values(cl[:Close][idx])) == values(cl_first[:Close][2])[1]
+        @test last(values(cl[:Close][idx])) == values(cl_last[:Close][2])[1]
+    end
+
+    @testset "Median aggregation" begin
+        new_timestamps = collect(Dates.Date(2000):Dates.Week(1):Dates.Date(2001))
+
+        cl_new = retime(cl, new_timestamps; downsample=:median)
+        @test timestamp(cl_new) == new_timestamps
+
+        # Verify median is correct
+        idx = new_timestamps[2] .<= timestamp(cl) .< new_timestamps[3]
+        @test median(values(cl[:Close][idx])) == values(cl_new[:Close][2])[1]
+    end
 end