erro com scale_x_labels no ggplot2

Estou tentando recriar os gráficos emeste livro usando ggplot2. Os dados que estou usando estão na parte inferior da postagem de umdput. Está disponível no site do editor. Estou recriando o gráfico de séries temporais na página 12.

Aqui está o código que estou usando:

y_min <- min(chartout$LCL)
y_max <- max(chartout$UCL)

ggplot() + 
        geom_line(mapping=aes(x=Date, y=Rate), data=chartout, size=1, alpha=0.5) +
        geom_point(data = chartout, mapping=aes(x=Date,y=Rate), size=3) +
        expand_limits(y = c(y_min, y_max)) +
        geom_line(mapping=aes(x=Date, y=UCL), data=chartout, colour='red',  size=1, alpha=0.5) + 
        geom_line(mapping=aes(x=Date, y=LCL), data=chartout, colour='red' , size=1, alpha=0.5) +
        scale_x_date(labels = date_format("%m %d")) +
        theme_bw()

O problema é que eu recebo o seguinte erro:

Erro: Entrada inválida: date_trans funciona apenas com objetos da classe Data

eu já viessa questão mas você pode ver a partir da estrutura nodput que a data está em um formato de data. Eu sei disso porque eu o convertei usandolubridate.

Alguma idéia de como corrigir isso?

saída de saída aqui:

chartout <- structure(list(Rate = c(0.2558, 0.2351, 0.4804, 0.2357, 0.2262, 
0.0433, 0.0839, 0.0422, 0.2569, 0.1283, 0.045, 0.2418, 0.3373, 
0.3214, 0.3026, 0.1307, 0.2986, 0.0431, 0.1259, 0.3339, 0.0432, 
0.2083, 0.3861, 0.0461, 0.4428, 0.1368, 0.3212, 0.1766, 0.1643, 
0.2503, 0.2033, 0.1199, 0.2084, 0.161, 0.3729, 0.4103, 0.4315, 
0.2195, 0.3619, 0.1698, 0.2368, 0.3717, 0.1943, 0.3199, 0.2495, 
0.3587, 0.1673, 0.3028, 0.2572, 0.2976, 0.4033, 0.2813, 0.3966, 
0.1609), Mean = c(0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 
0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 
0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 
0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 
0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 
0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 
0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411, 0.2411
), Date = structure(c(1072915200, 1075593600, 1078099200, 1080777600, 
1083369600, 1086048000, 1088640000, 1091318400, 1093996800, 1096588800, 
1099267200, 1101859200, 1104537600, 1107216000, 1109635200, 1112313600, 
1114905600, 1117584000, 1120176000, 1122854400, 1125532800, 1128124800, 
1130803200, 1133395200, 1136073600, 1138752000, 1141171200, 1143849600, 
1146441600, 1149120000, 1151712000, 1154390400, 1157068800, 1159660800, 
1162339200, 1164931200, 1167609600, 1170288000, 1172707200, 1175385600, 
1177977600, 1180656000, 1183248000, 1185926400, 1188604800, 1191196800, 
1193875200, 1196467200, 1199145600, 1201824000, 1204329600, 1207008000, 
1209600000, 1212278400), class = c("POSIXct", "POSIXt"), tzone = "UTC"), 
    UCL = c(0.6601, 0.6397, 0.6227, 0.6403, 0.6306, 0.6208, 0.6137, 
    0.6151, 0.6183, 0.618, 0.6294, 0.6464, 0.6456, 0.6341, 0.6204, 
    0.6221, 0.6174, 0.6197, 0.6139, 0.6126, 0.6205, 0.6122, 0.6187, 
    0.6351, 0.6258, 0.6324, 0.6042, 0.6252, 0.6091, 0.6125, 0.6069, 
    0.6032, 0.6124, 0.6047, 0.611, 0.6324, 0.62, 0.6238, 0.6045, 
    0.6163, 0.6006, 0.6103, 0.5973, 0.6033, 0.6118, 0.6026, 0.6131, 
    0.6206, 0.6185, 0.6167, 0.6051, 0.6043, 0.6016, 0.6046), 
    LCL = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 
    0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 
    0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 
    0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L)), .Names = c("Rate", 
"Mean", "Date", "UCL", "LCL"), row.names = c(NA, -54L), class = "data.frame")

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