diff --git a/zshrc b/zshrc
index b8a45e9..c3f8756 100644
--- a/zshrc
+++ b/zshrc
@@ -710,6 +710,74 @@ function tirm() {
 	unset tirm_confirmation tirm_task_id
 }
 ## }}}
+## Modify the start of a time tracking {{{
+function tistart() {
+
+	# Define new_start empty by default
+	tistart_time_new_start=""
+
+	# Verify argument
+	case "${#}" in
+		1 )
+			## Get the first arg as time ID
+			tistart_time_id="${1}"
+			;;
+		2 )
+			## Get the first arg as time ID
+			tistart_time_id="${1}"
+
+			## Get the second arg as new start time for this track
+			tistart_time_new_start="${2}"
+			;;
+		* )
+			## Ask the user to choose an ID in time tracking from the yesterday {{{
+			timew summary from yesterday :ids || return 0
+
+			printf '%b' "Enter the ${MAGENTAB}ID${RESET} of the time tracking to modify : "
+			read -r tistart_time_id
+			## }}}
+			;;
+	esac
+
+	# If no time tracking exists with this ID, exit function {{{
+	if ! timew summary :year :ids | grep --quiet -- " @${tistart_time_id} "; then
+		printf '%b' "No available time tracking in the last year with ${REDB}${tistart_time_id}${RESET} ID."
+		return 1
+	fi
+	# }}}
+
+	# Get time tracking's description from all time tracking of this year
+	local tistart_time_desc=$(timew summary :year :ids | sed -n "s/.*@\(${tistart_time_id} .*\)/\1/p" | sed 's/   */ − /g')
+
+	# Get time tracking's start day from all time tracking
+	local tistart_time_start_day=$(timew export | sed -nE "s/^\{\"id\":${tistart_time_id},\"start\":\"([0-9]{4})([0-9]{2})([0-9]{2})T.*end.*/\1-\2-\3/p")
+
+	# Check or ask for new start time {{{
+	if [ -z "${tistart_time_new_start}" ]; then
+			printf '%b' "Enter the ${MAGENTAB}new start time${RESET} (or new date 'YYYY-MM-DD${REDB}T${RESET}HH:MM:SS'; default day is ${tistart_time_start_day}) for this time tracking : "
+			read -r tistart_time_new_start
+	fi
+	# }}}
+
+	printf '%b' "Change start time of \"${MAGENTAB}${tistart_time_desc}${RESET}\" to ${REDB}=> ${tistart_time_new_start} <=${RESET} [Y/n] ? "
+	read -r tistart_confirmation
+
+	# Check confirmation
+	if printf -- '%s' "${tistart_confirmation:=y}" | grep --quiet --word-regexp -- "y"; then
+		## If the new start time entered by user contains a "T" (user enter a dateTtime)
+		if printf -- '%s' "${tistart_time_new_start}" | grep --quiet -- "T"; then
+			printf '%b' "start time of ${tistart_time_desc} is now ${tistart_time_new_start}."
+			timew modify start @"${tistart_time_id}" "${tistart_time_new_start}" || return 0
+		else
+			printf '%b' "start time of ${tistart_time_desc} is now ${tistart_time_start_day}T${tistart_time_new_start}."
+			timew modify start @"${tistart_time_id}" "${tistart_time_start_day}T${tistart_time_new_start}" || return 0
+		fi
+	fi
+
+	# Unset defined variables
+	unset tistart_confirmation tistart_time_id tistart_time_new_start
+}
+## }}}
 ## Modify the end of a time tracking {{{
 function tiend() {