Q: How to use substr function to create a new file without creating a list instead I am trying to use the substr function to change the time in one of my files
I want the created_at times to be changed from mdy/hms to mdy only
substr(jointTweet2$created_at.x, 1,10)

Doing this works, but does not change the dates in my file
jointTweet2 <- substr(jointTweet2$created_at.x, 1,10)

Doing this creates a list instead
How can i just do the time change without creating a list ?
I attached under my data as taken via dput
structure(list(author_id = c("1000023272250118144", "1000030523270496262", 
"1000043409212674048", "1000050535649759232", "1000051189986177025", 
"1000060938463170560"), possibly_sensitive = c(FALSE, FALSE, 
FALSE, TRUE, FALSE, FALSE), created_at.x = c("2021-06-13T01:42:23.000Z", 
"2021-02-10T17:55:43.000Z", "2021-04-09T22:31:24.000Z", "2021-04-19T16:11:28.000Z", 
"2021-01-11T10:06:43.000Z", "2021-01-16T11:30:34.000Z"), lang = c("en", 
"en", "en", "en", "en", "en"), source = c("Twitter Web App", 
"Twitter Web App", "Twitter Web App", "Twitter Web App", "Twitter for Android", 
"Twitter Web App"), public_metrics.x = structure(list(retweet_count = c(0L, 
1L, 4L, 4L, 0L, 27L), reply_count = c(0L, 0L, 1L, 0L, 0L, 5L), 
    like_count = c(1L, 0L, 5L, 39L, 0L, 125L), quote_count = c(0L, 
    0L, 0L, 0L, 0L, 0L)), row.names = c(302733L, 69371L, 179801L, 
198715L, 15735L, 24450L), class = "data.frame"), id = c("1403890461387919362", 
"1359561699733430273", "1380649576164642817", "1384177838757072906", 
"1348572038705733635", "1350405079216640003"), entities.x = structure(list(
    hashtags = list(structure(list(), .Names = character(0)), 
        structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
        structure(list(start = c(13L, 22L, 33L, 43L, 53L, 63L, 
        74L), end = c(21L, 32L, 42L, 52L, 62L, 73L, 78L), tag = c("gamedev", 
        "gamemaker", "pixelart", "aseprite", "indiedev", "indiegame", 
        "art")), class = "data.frame", row.names = c(NA, 7L)), 
        structure(list(), .Names = character(0)), structure(list(
            start = c(21L, 32L, 38L, 45L, 54L, 64L), end = c(31L, 
            37L, 44L, 53L, 63L, 69L), tag = c("IndieGame", "jRPG", 
            "RM2k3", "RPG<U+30C4><U+30AF><U+30FC><U+30EB>", "PixelArt", 
            "<U+30C9><U+30C3><U+30C8><U+7D75>")), class = "data.frame", row.names = c(NA, 
        6L))), urls = list(structure(list(start = 62L, end = 85L, 
        url = "", expanded_url = "", 
        display_url = ""), class = "data.frame", row.names = 1L), 
        structure(list(start = 197L, end = 220L, url = "", 
            expanded_url = "https://twitter.com/FroppleStudios/status/1359552958309019653", 
            display_url = ""), class = "data.frame", row.names = 1L), 
        structure(list(start = c(23L, 55L, 101L, 154L, 222L), 
            end = c(46L, 78L, 124L, 177L, 245L), url = c(""
            ), expanded_url = c(""), display_url = c(""
            ), status = c(NA, NA, 200L, NA, NA), unwound_url = c(NA, 
            NA, "", 
            NA, NA)), class = "data.frame", row.names = c(NA, 
        5L)), structure(list(start = 79L, end = 102L, url = "", 
            expanded_url = "", 
            display_url = "", media_key = "7_1384177629943590919"), class = "data.frame", row.names = 1L), 
        structure(list(start = 50L, end = 73L, url = "", 
            expanded_url = "", 
            display_url = ""), class = "data.frame", row.names = 1L), 
        structure(list(start = 70L, end = 93L, url = "", 
            expanded_url = "", 
            display_url = "", media_key = "3_1350404601623830529"), class = "data.frame", row.names = 1L)), 
    annotations = list(structure(list(), .Names = character(0)), 
        structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
        structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
        structure(list(), .Names = character(0))), mentions = list(
        structure(list(start = 90L, end = 98L, username = "YouTube", 
            id = "10228272"), class = "data.frame", row.names = 1L), 
        structure(list(start = 34L, end = 49L, username = "FroppleStudios", 
            id = "1359175250156679171"), class = "data.frame", row.names = 1L), 
        structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
        structure(list(start = 4L, end = 15L, username = "TimBledsoe", 
            id = "20614993"), class = "data.frame", row.names = 1L), 
        structure(list(), .Names = character(0))), cashtags = list(
        NULL, NULL, NULL, NULL, NULL, NULL)), row.names = c(302733L, 
69371L, 179801L, 198715L, 15735L, 24450L), class = "data.frame"), 
    conversation_id = c("1403890461387919362", "1359561699733430273", 
    "1380649576164642817", "1384177838757072906", "1348572038705733635", 
    "1350405079216640003"), text = c("RoboDunk - Reveal Trailer  Roguelite Basketball Combat for PC  via @YouTube", 
    "Currently working on a project at @FroppleStudios \nThose interested in following the development of an indie game be sure to follow. We are still in early stages but we will show more when we can. ", 
    "My stuff: Wood carving and Crafting Also you can check my brother's work here: He's making a cool indie game", 
    "Gutter ways\n\n#gamedev #gamemaker #pixelart #aseprite #indiedev #indiegame #art ", 
    "Hey @TimBledsoe here's a new indie game for you.  ", 
    "Mountainous ridge <U+0001F332>\n\n#IndieGame #jRPG #RM2k3 #RPG<U+30C4><U+30AF><U+30FC><U+30EB> #PixelArt #<U+30C9><U+30C3><U+30C8><U+7D75> "
    ), attachments = structure(list(media_keys = list(structure(list(), .Names = character(0)), 
        structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
        "7_1384177629943590919", structure(list(), .Names = character(0)), 
        "3_1350404601623830529"), poll_ids = list(structure(list(), .Names = character(0)), 
        NULL, structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
        structure(list(), .Names = character(0)), NULL)), row.names = c(302733L, 
    69371L, 179801L, 198715L, 15735L, 24450L), class = "data.frame"), 
    geo = structure(list(place_id = c(NA_character_, NA_character_, 
    NA_character_, NA_character_, NA_character_, NA_character_
    ), coordinates = structure(list(coordinates = list(NULL, 
        NULL, NULL, NULL, NULL, NULL), type = c(NA_character_, 
    NA_character_, NA_character_, NA_character_, NA_character_, 
    NA_character_)), row.names = c(302733L, 69371L, 179801L, 
    198715L, 15735L, 24450L), class = "data.frame")), row.names = c(302733L, 
    69371L, 179801L, 198715L, 15735L, 24450L), class = "data.frame"), 
    referenced_tweets = list(structure(list(), .Names = character(0)), 
        structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
        structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
        structure(list(), .Names = character(0))), `FTweet$id` = c("1403890461387919362", 
    "1359561699733430273", "1380649576164642817", "1384177838757072906", 
    "1348572038705733635", "1350405079216640003"), created_at.y = c("2018-05-25T14:38:22.000Z", 
    "2018-05-25T15:07:11.000Z", "2018-05-25T15:58:23.000Z", "2018-05-25T16:26:42.000Z", 
    "2018-05-25T16:29:18.000Z", "2018-05-25T17:08:02.000Z"), 
    verified = c(FALSE, FALSE, FALSE, FALSE, FALSE, FALSE), protected = c(FALSE, 
    FALSE, FALSE, FALSE, FALSE, FALSE), public_metrics.y = structure(list(
        followers_count = c(58L, 38L, 304L, 1444L, 4003L, 3696L
        ), following_count = c(27L, 323L, 255L, 531L, 273L, 1806L
        ), tweet_count = c(2721L, 7212L, 6082L, 663L, 11167L, 
        1531L), listed_count = c(2L, 0L, 1L, 21L, 55L, 53L)), row.names = c("56366", 
    "20397", "39153", "41987", "7173", "9740"), class = "data.frame"), 
    entities.y = structure(list(url = structure(list(urls = list(
        structure(list(start = 0L, end = 23L, url = "", 
            expanded_url = "", display_url = "oldgamers.net"), class = "data.frame", row.names = 1L), 
        structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
        structure(list(), .Names = character(0)), structure(list(
            start = 0L, end = 23L, url = "", 
            expanded_url = "", display_url = "castjunkie.com"), class = "data.frame", row.names = 1L), 
        structure(list(start = 0L, end = 23L, url = "", 
            expanded_url = "", 
            display_url = ""), class = "data.frame", row.names = 1L))), row.names = c("56366", 
    "20397", "39153", "41987", "7173", "9740"), class = "data.frame"), 
        description = structure(list(urls = list(structure(list(
            start = 87L, end = 110L, url = "", 
            expanded_url = "", display_url = ""), class = "data.frame", row.names = 1L), 
            structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
            structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
            structure(list(), .Names = character(0))), hashtags = list(
            structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
            structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
            structure(list(start = 80L, end = 101L, tag = "SupportIndiePodcasts"), class = "data.frame", row.names = 1L), 
            structure(list(), .Names = character(0))), mentions = list(
            structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
            structure(list(start = 74L, end = 85L, username = "Callia_wen"), class = "data.frame", row.names = 1L), 
            structure(list(), .Names = character(0)), structure(list(), .Names = character(0)), 
            structure(list(start = 7L, end = 22L, username = "BelovedRapture"), class = "data.frame", row.names = 1L)), 
            cashtags = list(NULL, NULL, structure(list(), .Names = character(0)), 
                NULL, structure(list(), .Names = character(0)), 
                NULL)), row.names = c("56366", "20397", "39153", 
        "41987", "7173", "9740"), class = "data.frame")), row.names = c("56366", 
    "20397", "39153", "41987", "7173", "9740"), class = "data.frame"), 
    username = c("oldgamers_TV", "DavidSantosDev", "Senti_nelle", 
    "_AERYS_", "castjunkie", "BelovedRapture"), location = c("Houston, TX", 
    NA, "Mon PV : @JeanJean_PV", "Northern Ireland", "Washington, USA", 
    "Boston, MA"), description = c("Oldgamers shares gaming news & Support streamers.\nAd* Video Games Best Deals are here: ", 
    "", "Artisan de l'art. <U+2606> I draw big mechas, dragons and OCs\nHunting partner of @Callia_wen", 
    "Game Developer | 20 | UK | Thank You All So Much For 1400 Followers! Big fan of Adventure Time. Commissions open :D", 
    "Host of vibrant Discord community with thousands of podcast creators/listeners. #SupportIndiePodcasts", 
    "Dev of @BelovedRapture, a SNES-styled indie RPG game. <U+0001F3AE><U+0001F3F3><U+FE0F><U+200D><U+0001F308><U+0001F338>"
    ), pinned_tweet_id = c(NA, NA, "1380649576164642817", NA, 
    "1515503033177673729", "1455620363564556291"), name = c("oldgamers_TV", 
    "David", "Sentinelle <U+0001F47A>", "Aerys", "CastJunkie", 
    "Blind"), withheld = structure(list(country_codes = list(
        NULL, NULL, NULL, NULL, NULL, NULL)), row.names = c("56366", 
    "20397", "39153", "41987", "7173", "9740"), class = "data.frame"), 
    `FUsers$id` = c("1000023272250118144", "1000030523270496262", 
    "1000043409212674048", "1000050535649759232", "1000051189986177025", 
    "1000060938463170560")), row.names = c(NA, 6L), class = "data.frame")

Sorry for all the added data, i hope it works
I had to remove the URL's by hand

A: Managed to fix it using the following function:
system.time(jointTweet2$created_at.x <- as.Date(jointTweet2$created_at.x))

No idea why the rest was not working
