diff --git a/R/write_dataset_json.R b/R/write_dataset_json.R
index 448764d..3d490a7 100644
--- a/R/write_dataset_json.R
+++ b/R/write_dataset_json.R
@@ -34,19 +34,27 @@
 #' \dontrun{
 #'   write_dataset_json(ds_json, "path/to/file.json")
 #' }
-write_dataset_json <- function(x, file, pretty=FALSE, float_as_decimals=FALSE, digits=16) {
+write_dataset_json <- function(
+  x,
+  file,
+  pretty = FALSE,
+  float_as_decimals = FALSE,
+  digits = 16
+) {
   stopifnot_datasetjson(x)
 
   meta <- attributes(x)
 
   # Find all date, datetime and time columns and convert to character
   for (i in seq_along(meta$columns)) {
-
-
     y <- meta$columns[[i]]
 
     # Make sure metadata is compliant
-    if (y$dataType %in% c("date", "datetime", "time") & !("targetDataType" %in% names(y))) {
+    if (
+      y$dataType %in%
+        c("date", "datetime", "time") &
+        !("targetDataType" %in% names(y))
+    ) {
       if (!inherits(x[[y$name]], "character")) {
         stop_write_error(
           y$name,
@@ -55,35 +63,57 @@ write_dataset_json <- function(x, file, pretty=FALSE, float_as_decimals=FALSE, d
       }
     }
 
-    if(y$dataType %in% c("date", "datetime", "time") & (!is.null(y$targetDataType) && y$targetDataType == "integer")) {
+    if (
+      y$dataType %in%
+        c("date", "datetime", "time") &
+        (!is.null(y$targetDataType) && y$targetDataType == "integer")
+    ) {
       # Convert date
       if (y$dataType == "date") {
-        x[y$name] <- format(x[[y$name]], "%Y-%m-%d", tz='UTC')
+        x[y$name] <- format(x[[y$name]], "%Y-%m-%d", tz = 'UTC')
       }
 
       # Convert datetime
       if (y$dataType == "datetime") {
         # Ensure type and timezone is right.
-        if (!inherits(x[[y$name]], "POSIXt") || !("UTC" %in% attr(x[[y$name]], 'tzone'))){
-          stop_write_error(y$name, "Date time variable must be provided as POSIXlt type with timezone set to UTC.")
+        if (
+          !inherits(x[[y$name]], "POSIXt") ||
+            !("UTC" %in% attr(x[[y$name]], 'tzone'))
+        ) {
+          stop_write_error(
+            y$name,
+            "Date time variable must be provided as POSIXlt type with timezone set to UTC."
+          )
         }
-        x[y$name] <- strftime(x[[y$name]], "%Y-%m-%dT%H:%M:%S", tz='UTC')
+        x[y$name] <- strftime(x[[y$name]], "%Y-%m-%dT%H:%M:%S", tz = 'UTC')
       }
 
       # Convert time
       if (y$dataType == "time") {
-        if (y$dataType == "time" & !inherits(x[[y$name]], c("Period", "difftime", "ITime"))) {
+        if (
+          y$dataType == "time" &
+            !inherits(x[[y$name]], c("Period", "difftime", "ITime"))
+        ) {
           stop_write_error(
             y$name,
             "If dataType is time and targetDataType is integer, the input variable type must be a lubridate Period, an hms difftime, or a data.table ITime object"
           )
         }
-        x[y$name] <- strftime(as.numeric(x[[y$name]]), "%H:%M:%S", tz='UTC')
+        x[y$name] <- strftime(
+          as.POSIXlt(
+            as.numeric(x[[y$name]]),
+            tz = 'UTC',
+            origin = "1970-01-01"
+          ),
+          "%H:%M:%S",
+        )
       }
-    } else if (float_as_decimals && y$dataType %in% c("float", 'double', 'decimal')) {
+    } else if (
+      float_as_decimals && y$dataType %in% c("float", 'double', 'decimal')
+    ) {
       meta$columns[[i]]['dataType'] <- "decimal"
       meta$columns[[i]]['targetDataType'] <- "decimal"
-      x[y$name] <- format(x[y$name], digits=digits)
+      x[y$name] <- format(x[y$name], digits = digits)
     }
   }
 
@@ -109,8 +139,8 @@ write_dataset_json <- function(x, file, pretty=FALSE, float_as_decimals=FALSE, d
     "records",
     "name",
     "label",
-    "columns")
-    ]
+    "columns"
+  )]
 
   temp <- remove_nulls(temp)
 
@@ -119,8 +149,8 @@ write_dataset_json <- function(x, file, pretty=FALSE, float_as_decimals=FALSE, d
 
   if (!missing(file)) {
     # Make sure the output path exists
-    if(!dir.exists(dirname(file))) {
-      stop("Folder supplied to `file` does not exist", call.=FALSE)
+    if (!dir.exists(dirname(file))) {
+      stop("Folder supplied to `file` does not exist", call. = FALSE)
     }
   }
 
@@ -146,12 +176,15 @@ write_dataset_json <- function(x, file, pretty=FALSE, float_as_decimals=FALSE, d
   }
 }
 
-stop_write_error <- function(varname, msg){
+stop_write_error <- function(varname, msg) {
   stop(
-    sprintf(paste(
-      "Please check the variable %s.",
-      msg,
-      sep="\n  "),
-      varname)
+    sprintf(
+      paste(
+        "Please check the variable %s.",
+        msg,
+        sep = "\n  "
+      ),
+      varname
+    )
   )
 }