diff --git a/libsrc/common/asctime.c b/libsrc/common/asctime.c
deleted file mode 100644
index b46f29128..000000000
--- a/libsrc/common/asctime.c
+++ /dev/null
@@ -1,59 +0,0 @@
-/*****************************************************************************/
-/*                                                                           */
-/*                                   asctime.c                               */
-/*                                                                           */
-/*                 Convert a broken down time into a string                  */
-/*                                                                           */
-/*                                                                           */
-/*                                                                           */
-/* (C) 2002      Ullrich von Bassewitz                                       */
-/*               Wacholderweg 14                                             */
-/*               D-70597 Stuttgart                                           */
-/* EMail:        uz@musoftware.de                                            */
-/*                                                                           */
-/*                                                                           */
-/* This software is provided 'as-is', without any expressed or implied       */
-/* warranty.  In no event will the authors be held liable for any damages    */
-/* arising from the use of this software.                                    */
-/*                                                                           */
-/* Permission is granted to anyone to use this software for any purpose,     */
-/* including commercial applications, and to alter it and redistribute it    */
-/* freely, subject to the following restrictions:                            */
-/*                                                                           */
-/* 1. The origin of this software must not be misrepresented; you must not   */
-/*    claim that you wrote the original software. If you use this software   */
-/*    in a product, an acknowledgment in the product documentation would be  */
-/*    appreciated but is not required.                                       */
-/* 2. Altered source versions must be plainly marked as such, and must not   */
-/*    be misrepresented as being the original software.                      */
-/* 3. This notice may not be removed or altered from any source              */
-/*    distribution.                                                          */
-/*                                                                           */
-/*****************************************************************************/
-
-
-
-#include <stdio.h>
-#include <time.h>
-
-
-
-/*****************************************************************************/
-/*                                   Code                                    */
-/*****************************************************************************/
-
-/*
-    CAUTION: we need to reserve enough space to be able to hold the maximum
-    length string:
-
-     1234567890123456789012345678901234567
-    "Wednesday September ..1 00:00:00 1970"
-*/
-
-char* __fastcall__ asctime (const struct tm* timep)
-{
-    static char buf[38];
-
-    /* Format into given buffer and return the result */
-    return strftime (buf, sizeof (buf), "%c\n", timep)? buf : 0;
-}
diff --git a/libsrc/common/asctime.s b/libsrc/common/asctime.s
new file mode 100644
index 000000000..efcf34b41
--- /dev/null
+++ b/libsrc/common/asctime.s
@@ -0,0 +1,81 @@
+;
+; Colin Leroy-Mira, 2024
+;
+; char* __fastcall__ asctime (const struct tm* timep)
+;
+
+        .export         _asctime
+        .import         _strftime, pushax
+        .importzp       ptr1
+        .include        "time.inc"
+
+        .macpack        cpu
+
+; ------------------------------------------------------------------------
+; Special values
+
+; We need to be able to store up to 38 bytes:
+;     1234567890123456789012345678901234567
+;    "Wednesday September ..1 00:00:00 1970"
+MAX_BUF_LEN = 38
+
+; ------------------------------------------------------------------------
+; Code
+
+_asctime:
+        ; Backup timep
+        .if (.cpu .bitand ::CPU_ISET_65SC02)
+        pha
+        phx
+        .else
+        sta     ptr1
+        stx     ptr1+1
+        .endif
+
+        ; Push buf
+        lda     #<buf
+        ldx     #>buf
+        jsr     pushax
+
+        ; Push sizeof(buf)
+        lda     #<MAX_BUF_LEN
+        ldx     #>MAX_BUF_LEN
+        jsr     pushax
+
+        ; Push format string
+        lda     #<fmt
+        ldx     #>fmt
+        jsr     pushax
+
+        ; Restore timep
+        .if (.cpu .bitand ::CPU_ISET_65SC02)
+        plx
+        pla
+        .else
+        lda     ptr1
+        ldx     ptr1+1
+        .endif
+
+        ; Call formatter
+        jsr     _strftime
+
+        ; Check return status
+        bne     :+
+        cpx     #$00
+        bne     :+
+        rts
+
+:       lda     #<buf
+        ldx     #>buf
+        rts
+
+        .data
+
+fmt:    .byte '%'
+        .byte 'c'
+        .byte $0A
+        .byte $00
+
+        .bss
+
+buf:    .res MAX_BUF_LEN